# prioritizing energy savings - spray foam vs. wood stove



## twd000 (Mar 7, 2016)

I'm trying to decide where to invest my dollars to save money on the "whole picture" of my home's energy use.

It's a 1974 colonial in Southern New Hampshire, USDA Zone 4.  3000 square feet of conditioned space. Propane furnace in winter, central air conditioning used sparingly in the summer.  At current energy prices, yearly total spending is about
$1600 electricity
$900 water heating
$1900 space heating

I estimate I'm using 60 MBTU per year for space heating.  I think it is reasonably well insulated, new windows etc.  But I don't believe any effort was made for air-sealing the attic, basement, top plates, plus all the little passthroughs for bathroom vents, HVAC ducts, etc.

So I'm trying to evaluate two projects:

Removing all the fiberglass and cellulose attic insulation and having it sprayed with closed-cell spray foam.  There are two rooflines, with 1400 sq ft total attic space.  My ballpark estimate is $8,000 for 6" R-42 equivalent.


installing a Blaze King King in the main living floor, plus stainless liner and some non-trivial chimney modification.  I'm estimating $6,000.
Of course I'll get professional estimates once I decide which project to proceed with.
My payback estimate on the stove is 4-5 years.  Has anyone gone down the road of spray foam in existing construction, to estimate the payback period?  And how much I should expect my yearly MBTU to be reduced?  The spray foam is appealing because it helps during heating and cooling season.  But I don't know if the marginal efficiency increase is justified.


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## BKVP (Mar 7, 2016)

twd000 said:


> I'm trying to decide where to invest my dollars to save money on the "whole picture" of my home's energy use.
> 
> It's a 1974 colonial in Southern New Hampshire, USDA Zone 4.  3000 square feet of conditioned space. Propane furnace in winter, central air conditioning used sparingly in the summer.  At current energy prices, yearly total spending is about
> $1600 electricity
> ...


I say go for the King!  My grandkids need a college fund!


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## twd000 (Mar 7, 2016)

Well I know you wouldn't want your grandkids to get spoiled, so how about I pay them $15/hour to come spray foam my attic!?


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## begreen (Mar 7, 2016)

What would be your source of wood? Purchased or home cut, split and stacked? If home C/S/S do you already have the equipment to do this? 

How much insulation is currently in the attic?


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## peakbagger (Mar 7, 2016)

Its a no brainer, insulate first and then install a stove. The best BTUs are the one you don't have to burn. Look into this program and get the utility to pay for a big chunk of it
http://www.nhsaves.com/save-home/save-more/energy-audits-weatherization/.  I did flash and bat on half my attic, it was fairly new insulation so I pulled it and had them spray about 3" of foam then put the insulation back in place with a second layer running cross ways to the first. On the other side they pulled the fiberglass in few spots but mostly sealed  few light fixtures. The only down side is I lost attic storage space as the insulation is up on the rafters. One of these days I will probably put in elevated gangplanks. The biggest bang for the buck was they sprayed my basement sills and sealed some can lights. 

Next thing is find a wood supply a year to two years before you buy a stove and get it cut split and piled up and dying, then watch craigslist and uncle henry's for the suckers who are yanking out new stoves thinking the cost for oil or gas is going to stay low (or were trying to burn green wood with an EPA stove).


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## BKVP (Mar 7, 2016)

twd000 said:


> Well I know you wouldn't want your grandkids to get spoiled, so how about I pay them $15/hour to come spray foam my attic!?


Hey, that's minimum wage in Seattle.  My 4 year old granddaughter would do it in a heart-beat...and her 7 year old brother would watch her!


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## twd000 (Mar 7, 2016)

begreen said:


> What would be your source of wood? Purchased or home cut, split and stacked? If home C/S/S do you already have the equipment to do this?
> 
> How much insulation is currently in the attic?



I would estimate there is an average of 12" of insulation across the attic. It's pretty haphazard. I assume all the rafter bays are filled with fiberglass, then there is some blown in cellulose on top of that in some areas, but not others. Some areas also have batts laid crosswise on top of the other batts.

I am looking at having log length cord wood delivered at $125 a cord. I was surprised at how little scrounging shortened the payback period. Yes I have all the equipment to process it onsite, and I have about 3 cords ready to go.


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## twd000 (Mar 7, 2016)

peakbagger said:


> Its a no brainer, insulate first and then install a stove. The best BTUs are the one you don't have to burn. Look into this program and get the utility to pay for a big chunk of it
> http://www.nhsaves.com/save-home/save-more/energy-audits-weatherization/.  I did flash and bat on half my attic, it was fairly new insulation so I pulled it and had them spray about 3" of foam then put the insulation back in place with a second layer running cross ways to the first. On the other side they pulled the fiberglass in few spots but mostly sealed  few light fixtures. The only down side is I lost attic storage space as the insulation is up on the rafters. One of these days I will probably put in elevated gangplanks. The biggest bang for the buck was they sprayed my basement sills and sealed some can lights.



Thanks for the program info. Can you give me some numbers on your project?  Energy usage before and after?


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## begreen (Mar 7, 2016)

twd000 said:


> I would estimate there is an average of 12" of insulation across the attic. It's pretty haphazard. I assume all the rafter bays are filled with fiberglass, then there is some blown in cellulose on top of that in some areas, but not others. Some areas also have batts laid crosswise on top of the other batts.
> 
> I am looking at having log length cord wood delivered at $125 a cord. I was surprised at how little scrounging shortened the payback period. Yes I have all the equipment to process it onsite, and I have about 3 cords ready to go.


Sounds like you know the riff and are ready for wood heat. Both options are going to return nice gains. I'd be tempted to insulate first for year round benefit and put in a <$1000 stove now like the Drolet Myriad or Englander 30NC. Upgrade in a few years as the budget permits.


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## brenndatomu (Mar 7, 2016)

begreen said:


> Sounds like you know the riff and are ready for wood heat. Both options are going to return nice gains. I'd be tempted to insulate first for year round benefit and put in a <$1000 stove now like the Drolet Myriad or Englander 30NC. Upgrade in a few years as the budget permits.


Yes, this ^ ^ ^


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## peakbagger (Mar 8, 2016)

I really cant give you true payback on my project as I had a couple of other energy projects that were done in at the same time. I live in northern NH and have not filled my oil tank in three years. I use a minisplit for my only heating source when averages temps are around 30 and used 3.5 cords last year and around a cord and half this winter. I generate excess electric power with my solar but figure I use about 1800 kw for the minisplit.

The nice thing with the NH program is the utility audits the work and the contractor does a pre and post blower door test.  When they do the audit they will hand you the report with the payback for each improvement. The biggest payback  is air sealing.


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## semipro (Mar 8, 2016)

Any opportunity to connect your furnace to natural gas?  

Conservation versus woodstove: with the first, get it done and enjoy; if you install a stove the work is only beginning.   
If you take all the time and money you'd spend heating with wood and instead seal and insulate the house you'll be way ahead in a few years with lasting benefits.  You can then install a smaller wood stove, HP, whatever for heating.


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## BKVP (Mar 8, 2016)

Think of all the exercise you will get cutting, splitting and stacking...and then loading too!  Heck, you're saving the money a gym membership would cost you.


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## LowbanksArcher (Mar 8, 2016)

twd000 said:


> I would estimate there is an average of 12" of insulation across the attic. It's pretty haphazard. I assume all the rafter bays are filled with fiberglass, then there is some blown in cellulose on top of that in some areas, but not others. Some areas also have batts laid crosswise on top of the other batts.
> 
> I am looking at having log length cord wood delivered at $125 a cord. I was surprised at how little scrounging shortened the payback period. Yes I have all the equipment to process it onsite, and I have about 3 cords ready to go.



12" of cellulose and/or fibreglass puts your R value in the mid 30's. (both fiberglass and cellulose have an R value slightly over R3 per inch). If it were me, I'd have additional cellulose blown in to have even insulation in the whole attic and correct those 'haphazard' areas. At a fraction of the cost of spray foam. 
Then add your stove.


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## Circus (Mar 8, 2016)

Changing the attic insulation won't do anything. Sealing the attic will only cause moisture problems.  The reason people always harp about attic insulation is because it's accessible. Even a poorly insulated attic, say 6" fiberglass, only accounts for 20% heat loss.


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## twd000 (Mar 8, 2016)

semipro said:


> Any opportunity to connect your furnace to natural gas?
> 
> Conservation versus woodstove: with the first, get it done and enjoy; if you install a stove the work is only beginning.
> If you take all the time and money you'd spend heating with wood and instead seal and insulate the house you'll be way ahead in a few years with lasting benefits.  You can then install a smaller wood stove, HP, whatever for heating.



no natural gas available in my area; most people with propane installed it for backup generators, then switched their furnace from oil to propane.  It looks like prior owners of my house took the same approach.

Yes, the passive aspect of air sealing is appealing.  I'm looking into the audit/rebate now


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## twd000 (Mar 8, 2016)

peakbagger said:


> I really cant give you true payback on my project as I had a couple of other energy projects that were done in at the same time. I live in northern NH and have not filled my oil tank in three years. I use a minisplit for my only heating source when averages temps are around 30 and used 3.5 cords last year and around a cord and half this winter. I generate excess electric power with my solar but figure I use about 1800 kw for the minisplit.
> 
> The nice thing with the NH program is the utility audits the work and the contractor does a pre and post blower door test.  When they do the audit they will hand you the report with the payback for each improvement. The biggest payback  is air sealing.



I assume you meant 1800 kWh for the minisplit heat pump?  If so that is about 10% of my yearly MBTU consumption. Plus 3.5 cords of oak (22 MBTU/cord , 70% efficiency) is another 110 MBTU.  You're definitely in a colder climate, and last winter was extreme.

I just ran the calculator at NHSaves.com.  It reports that my current propane consumption (20k BTU/sq ft) s already very efficient, and therefore I'm not eligible for audit/weatherization rebates.  I had to bump consumption up to 200 gallons/year to get into the inefficient zone of their calculator.  There must be some really leaky houses around here!


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## Highbeam (Mar 8, 2016)

LowbanksArcher said:


> 12" of cellulose and/or fibreglass puts your R value in the mid 30's. (both fiberglass and cellulose have an R value slightly over R3 per inch). If it were me, I'd have additional cellulose blown in to have even insulation in the whole attic and correct those 'haphazard' areas. At a fraction of the cost of spray foam.
> Then add your stove.



This is the answer. You already have better attic insulation than most. Moving up from mid R30s to R42 by removing your existing is a bad idea IMO. If you are just dying to get more R-value you can blow in more cellulose. I bet your walls are 2x4 construction with R-5 batts, R-13 at best. That's where you can increase the R-value that has some payback.


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## semipro (Mar 8, 2016)

LowbanksArcher said:


> 12" of cellulose and/or fibreglass puts your R value in the mid 30's. (both fiberglass and cellulose have an R value slightly over R3 per inch). If it were me, I'd have additional cellulose blown in to have even insulation in the whole attic and correct those 'haphazard' areas. At a fraction of the cost of spray foam.





Highbeam said:


> This is the answer. You already have better attic insulation than most. Moving up from mid R30s to R42 by removing your existing is a bad idea IMO. If you are just dying to get more R-value you can blow in more cellulose. I bet your walls are 2x4 construction with R-5 batts, R-13 at best. That's where you can increase the R-value that has some payback.


This does nothing for air sealing (isolating attic from living space) though which could well be your biggest heat loss because of stack effect.


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## peakbagger (Mar 8, 2016)

Bummer on the lack of rebate money, I was on the edge when I took advantage. You are correct 1800 KWhr. Even if the state wont do it, looks around for an organization with blower door. This group has one in Plymouth http://www.plymouthenergy.org/. Alternatively I expect you could rig up large house fan with tarp over the door opening. It really impressive how depressurizing a house on cold day shows where the leaks are. I finished a large master bedroom about 10 years ago and thought I did good job, once the blower was on I found that I had air coming in under the outerwall sills and my outlets. Of course I was also sucking air down the chimney.

They had to install a fan timer on my bathroom to force more air changes to meet indoor air quality. Its taken several years but I just bought a Fantech HRV and am in the process of collecting parts to install it.

Come on up to the Berlin, a lot of the old rental units have little or no insulation or poorly pumped in cellulose. Many have single pane windows and wooden doors with no weather stripping. Insulation is important but infiltration is the killer, A closed door with no weather-stripping is equivalent of good sized hole in the wall . A friend just built a Passivhaus in Portland Maine, its amazing the extent they had to go to seal the envelope so they are darn close to zero infiltration. They bring it way down and then add back in air where they need it via a  HRV.


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## Highbeam (Mar 8, 2016)

semipro said:


> This does nothing for air sealing (isolating attic from living space) though which could well be your biggest heat loss because of stack effect.



What I've done is complete the air sealing with the old insulation in place and then add additional cellulose to R-50. Sure, full spray foam is superior but at a ridiculous cost for an attic with access.


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## jebatty (Mar 9, 2016)

twd000 said:


> 3000 square feet of conditioned space....
> $1600 electricity
> $900 water heating
> $1900 space heating
> I  estimate I'm using 60 MBTU per year for space heating.


 What are your electric rates? 

By far, the least expensive energy saving is conservation. I would recommend that you consider pursuing conservation with a vengeance, something my wife and I have done. We also are in USDA Zone 4 and 3000 square feet of conditioned space, all electric house except wood stove in the living room.

$420 electricity for domestic hot water and space heating (6,000 kwh)
$600 for general service electricity (5,000 kwh)
4 cords of aspen stove wood for space heating, c/s/s from our land, about $700 if we would buy c/s (equivalent to about 16,000 kwh)

We don't actually pay for that electricity, as 100%+ of our electricity is provide by our solar PV system.


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## semipro (Mar 9, 2016)

Highbeam said:


> What I've done is complete the air sealing with the old insulation in place and then add additional cellulose to R-50. Sure, full spray foam is superior but at a ridiculous cost for an attic with access.


Which is exactly what I think the OP should consider doing.  Agreed on the spray foam.  My point was that adding more thermal insulation without air sealing wasn't the right course.  The problem is working around all the insulation already in place - not fun.


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## twd000 (Mar 9, 2016)

jebatty said:


> What are your electric rates?
> 
> By far, the least expensive energy saving is conservation. I would recommend that you consider pursuing conservation with a vengeance, something my wife and I have done. We also are in USDA Zone 4 and 3000 square feet of conditioned space, all electric house except wood stove in the living room.
> 
> ...



Total effective electric rate is $0.17/kWh
Here are my numbers in kWh for comparison:
space heating: 18,000 kWh (propane source)
water heating: 9,000 kWh (propane source)
electricity: 9,600 kWh

Wow how did you get your electricity use that low?!  I'm 2x your usage.  I was thinking of trying one of those Energy Detective devices to identify and reduce my base load.


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## woodgeek (Mar 10, 2016)

A question....did the OP want to sprayfoam the attic floor to get better airsealing, under the existing insulation, and then up the insulation to R-50 as needed (and keep the attic vented) OR to sprayfoam the roofline sealing the attic?

Also...there is HVAC in the attic, or just a couple ducts?

I would say that 60 MMBTU for 3000 sq ft in that climate is prob 3-4 BTU/sqft.degreeday, already better than I **guess** 80% of american homes.


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## twd000 (Mar 10, 2016)

woodgeek said:


> A question....did the OP want to sprayfoam the attic floor to get better airsealing, under the existing insulation, and then up the insulation to R-50 as needed (and keep the attic vented) OR to sprayfoam the roofline sealing the attic?



The former, not the latter.

The furnace and air handler are in the basement.  The duct work servicing the 2nd floor bedrooms runs through the attic


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## woodgeek (Mar 10, 2016)

twd000 said:


> The former, not the latter.
> 
> The furnace and air handler are in the basement.  The duct work servicing the 2nd floor bedrooms runs through the attic



Thanks for the clarification.  In practice, sprayfoaming the entire attic floor is overkill and too expensive, unless the ceiling below is something super leaky like planks.  If its drywall, you only need to seal the top plates.  Less insulation to move = less labor = cheaper.  Whether your outfit seals the cracks there with sprayfoam or caulk is IMO up to them.  I used caulk DIY.

If the ducts are well sealed (not leaky), then just bury them under the other insulation.  Done.


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## semipro (Mar 10, 2016)

Info on attic air-sealing
http://www.finehomebuilding.com/pages/how-to-air-seal-attic/


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## St. Coemgen (Mar 13, 2016)

Improving your insulation can help you reduce costs on both _heating_ in the winter, and _cooling_ in the summer. That is, improving insulation is a full 12 month investment that helps all year long.

If one really has to choose only one option or the other, if one can improve their insulation (including properly controlling the general air movement into or out of their house) that is usually the option one should select first.


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## OhioBurner© (Mar 13, 2016)

Circus said:


> The reason people always harp about attic insulation is because it's accessible.



A lot of folks favor doing insulation first, and yeah attic insulation is #1. My house is very poorly insulated and leaky. It's pretty much a lost cause. And probably 80% of my house has no attic, only the master bedroom and bathroom have attic space overhead and its real tight in there with my low pitch ceiling. Rest of my house is all cathedral, and over half of that is only around 3" thick with fiberglass and I am sure some of it is wet since the metal roof either condenses or leaks in spots. And I am not about to tear down nice tongue-n-groove or even just drywall to get to it. One room, which had no insulation between the ceiling and roof, I did tear down last year since it was one of the few remaining rooms that were very old plaster. But the rest of the more recently refinished rooms I'm pretty stuck with thin FG. I'd be better off trying to move to a new house than insulate and air seal this one.


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## semipro (Mar 14, 2016)

OhioBurner© said:


> A lot of folks favor doing insulation first, and yeah attic insulation is #1. My house is very poorly insulated and leaky. It's pretty much a lost cause. And probably 80% of my house has no attic, only the master bedroom and bathroom have attic space overhead and its real tight in there with my low pitch ceiling. Rest of my house is all cathedral, and over half of that is only around 3" thick with fiberglass and I am sure some of it is wet since the metal roof either condenses or leaks in spots. And I am not about to tear down nice tongue-n-groove or even just drywall to get to it. One room, which had no insulation between the ceiling and roof, I did tear down last year since it was one of the few remaining rooms that were very old plaster. But the rest of the more recently refinished rooms I'm pretty stuck with thin FG. I'd be better off trying to move to a new house than insulate and air seal this one.


You may want to consider an insulated, unvented roof conversion.  http://www.finehomebuilding.com/des...-details/an-unvented-superinsulated-roof.aspx


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## OhioBurner© (Mar 14, 2016)

semipro said:


> You may want to consider an insulated, unvented roof conversion.  http://www.finehomebuilding.com/des...-details/an-unvented-superinsulated-roof.aspx


For the part I remodeled (the old plaster room) I did that. There is no feasible way to ventilate (and insulate) a roof that has only 3" thick trusses with the ceiling/walls attached underneath. And the metal roof was brand new when we moved in I have no intentions of ripping it off for any other major remodel. It was ventilated only in that it is very leaky and not weather tight. At the ridge and down by the eaves there were gaps here and there you could see daylight through. No sheathing either btw. I filled the truss bays with 3.5" thick foam board and another 1.5" layer on the underside though I am only 2/3 done with that. I'm not sure if the newer side is really vented or not, as it is cathedral again, except over the bedroom/bathroom. There is a vent on the gable end but I think it is just decoration. There is some venting under the eves but it is a fake gambrel roof and the part of the eaves is actually part of the wall and not sure if it actually goes up into the small attic space over the bedroom. I don't see any ridge vents or any other way for air to escape.


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## cableman (Apr 2, 2016)

I just completed 2 attics in the house we just moved to, once it got cold i knew i had to do something.
1st i fixed and ran any wiring i needed to. Started great stuffing anything that was an air leak to the living space, ended up buying the pro gun and man that thing is so much better. I ended up sealing all top plates, wire holes, ac ducts and air handler.
After that i installed raft-r-mate in every bay cause the old insulation had blocked the air flow to the soffits. Picked up 32 rolls of r30 and rolled it opposite the beams in both attics. Close to r50 now!
I also great stuffed my basement sills.
My exterior outlets were drafty too, i pulled them all and siliconed the wire entry into the box then caulked the sheetrock around each box.
What a difference and how the house doesnt cool down as fast. I can only imagine how much someone would have charged me!


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## woodgeek (Apr 2, 2016)

cableman said:


> I can only imagine how much someone would have charged me!



About $2-3k for materials and $2-4k for labor


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## cableman (Apr 2, 2016)

Wow, cost me 700 or so


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## Seasoned Oak (Apr 2, 2016)

60 MBTU  for the season sounds about right even low for NH     70MBTU was average last time i checked. So if your already fairly well insulated i cant see huge savings there. Around here propane heat is about the most expensive heat there is. ID go with a different heat source. My house is poorly insulated but my heat source is so cheap it doesnt matter much. Check into the cheapest  fuel by cost per million BTUs . Could be pellets. All this is subjective of course results may vary.
Heating cost this winter season for me is roughly 
Space heating $600
Water heating $300
Electric         $1800               for 3000 Sf house, family of 6.


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## iron (Apr 4, 2016)

i'm curious about the concept of sealing along top plates where they meet the ceiling drywall. i, like others, have a low pitched roof and access to those tight corners would be downright painful. 

so, my question is: what exactly are you sealing here? is it just a product of wall penetrations you're trying to mitigate (outlet boxes, picture nail holes, etc)? if so, couldn't you just spray foam locally those areas? then, seal the easier-to-get-to spots in the attic (ceiling lights, interior walls, plumbing pipes, etc)?


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## woodgeek (Apr 4, 2016)

iron said:


> i'm curious about the concept of sealing along top plates where they meet the ceiling drywall. i, like others, have a low pitched roof and access to those tight corners would be downright painful.
> 
> so, my question is: what exactly are you sealing here? is it just a product of wall penetrations you're trying to mitigate (outlet boxes, picture nail holes, etc)? if so, couldn't you just spray foam locally those areas? then, seal the easier-to-get-to spots in the attic (ceiling lights, interior walls, plumbing pipes, etc)?



Drywallers are taught to leave a 1/8 to 1/4" gap between the drywall and plate.  Times the length of the gap, this results in an area that is an order of magnitude larger than the wiring and other penetrations.  In my house, this worked out out to several square feet (!) of opening.

As for the low pitch, the pros always have a 'little guy' designated this job.


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## iron (Apr 4, 2016)

sure, but the corners are taped and mudded? where is the air leak coming from?


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## cableman (Apr 4, 2016)

I didnt get my outer top plates just the wire hole there, atleast insulation is in those walls. Sealing the outlets up helped the outer walls. As far as the inner top plates go, i could see straight down the wall when i lifted the insulation! Then there was the shotty ac duct work install, i had an inch gap on 2 sides of the return vent, and many other areas needing attention


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## woodgeek (Apr 4, 2016)

iron said:


> sure, but the corners are taped and mudded? where is the air leak coming from?



The corners are taped and mudded, and the cavity space has free exchange to the attic.  That cavity space connects to the space under the floors, through hardwood floors into the interior, as well as exterior wall cavities, the attached garage, etc.

When I got my house, the dryer exhaust dumped into the attached garage.  All that moisture flowed into the framing cavity of the house, thence directly into the attic space and condensed onto the underside of the sheathing.


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## iron (Apr 4, 2016)

sorry, i must be missing something. 

drywall is either nailed/screwed to the studs. it runs from floor to ceiling save for some gaps at both ends (one is taped and mudded, the other has a floor next to it with base trim (usually). i just don't see how heated air from the inside of the house makes it into the stud cavities unless it's through outlet openings or some other wall penetration. the air is not going through the floors unless there's a utility going through. exterior air might get in depending on sheathing, but that goes straight to the attic and seems like it would help cycle air through there akin to soffit vents.

perhaps i'm just trying to convince myself not to crawl into tight, painful positions....


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## Where2 (Apr 4, 2016)

iron said:


> sure, but the corners are taped and mudded? where is the air leak coming from?



If there is a wire going through the top plate, there's probably also an outlet box in that wall cavity between the studs. The old steel boxes resemble swiss cheese with lots of holes in them providing plenty of ingress of fresh air to replace that which goes up and out the top plate. (new plastic boxes are somewhat better, but still not perfect) Further contributing to this air migration path is the gap at the floor between the flooring and the wall materials. When I started dissecting the walls of my house at 45.8°N, which had un-taped drywall seams behind the 1970's paneling, it was quite evident where the air had been flowing through the paneling and drywall following the path of least resistance. The house had previously used a wood stove for supplemental heat, which obviously didn't always have the best ventilation capability. Sure, there was foil faced pink fiberglass in the stud bays, but this house is built on a ridge and the wind last night made +18°F feel like -1°F. None of the seams in the foil are taped, so air moved where it was easiest to move. The traveling air left behind traces of soot where it tended to migrate the most frequently.

Dismantling the walls is actually rather telling in the case of the house I am working on. As someone who comes from the subtropical southern Florida region, I've never dealt with heating or heat loss to this extreme. It's a bad winter when it dips below freezing for a few hours where I grew up in FL. This has however opened my eyes to why my energy savings was so great when we opened the walls of the second floor of our house in FL and sealed the wire penetrations through the top plate. At the same time we cut 2" foil faced polyiso to fit between the studs, then sealed the gaps and edges with canned foam. Wish I could add 2" polyiso between the drywall and the concrete block wall in the lower story...


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## cableman (Apr 4, 2016)

I still have 2 cantlevers which leak air into 1st floor ceiling/2nd floors floor, that ill pull outside soffits and ridgid board the bays sealing off with more great stuff.
Every little air leak sealed is that much better.
Heres how i did 20 outer wall outlets, used a bic pen body taped to silicone so it was easier getting to the wire holes...


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## woodgeek (Apr 4, 2016)

In my experience, the baseboard covers the sloppy gap between bottom plates, subfloors, drywall etc.   And a lot of drywall in old houses has popped off the studs aways, studs are warped, etc.

Bottom line, house framing is only a bunch of separate airtight cavities on the drawings.  In reality, there are gaps connecting the cavities throughout most houses.


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## semipro (Apr 5, 2016)

woodgeek said:


> Bottom line, house framing is only a bunch of separate airtight cavities on the drawings. In reality, there are gaps connecting the cavities throughout most houses.


Agreed.  Which is why its difficult to have an impact on overall infiltration by addressing leaks at interior points like outlets, baseboard areas, and around windows and doors.   Blower door tests done before and after such efforts have shown little improvement in overall air-tightness.
Airtight drywall can be done and is commonly done in Europe.  In this case the infiltration barrier is established on the interior shell of the house.  However, its very difficult to seal drywall that's not built as "airtight" from the beginning.
Rather than sealing random accessible interior and exterior air passage points a better strategy is to pick either an interior or exterior "plane" as your shell for air sealing and concentrate you efforts on that alone.


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## semipro (Apr 5, 2016)

Every time threads like this come up I like to relate the experience of working with a pro canned foam gun rather than the one-use cans.  
https://www.hearth.com/talk/threads/multi-use-foam-applicator-gun-follow-up.107613/#post-1422912


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## Highbeam (Apr 5, 2016)

iron said:


> sorry, i must be missing something.
> 
> drywall is either nailed/screwed to the studs. it runs from floor to ceiling save for some gaps at both ends (one is taped and mudded, the other has a floor next to it with base trim (usually). i just don't see how heated air from the inside of the house makes it into the stud cavities unless it's through outlet openings or some other wall penetration. the air is not going through the floors unless there's a utility going through. exterior air might get in depending on sheathing, but that goes straight to the attic and seems like it would help cycle air through there akin to soffit vents.
> 
> perhaps i'm just trying to convince myself not to crawl into tight, painful positions....



I've actually hung drywall. I've also had the same question. Sure, you leave the ceiling sheetrock 1/8" to 1/4" shy of the top plate for the sake of installation but when you put the wall sheetrock up you push it up tight to the ceiling rock and then attach it tightly to the top plate every 6". You then mud and tape this inside corner.

The "leaks" being solved by foaming the top plate in the attic are of course the actual wire penetrations but also the failure of your 6" OC top plate attachment screws to hold the wall rock tight to the top plate. I don't see this as being a very likely leak. Flow throuh this leak also depends on a separate leak occurring elsewhere in the wall at an outlet or penetration in the wall to allow air to enter the wall cavity before existing through this theoretical top plate leak.

Get the wire penetrations for sure.


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## woodgeek (Apr 5, 2016)

Let's be empirical....

When I am in my attic, I can look into the gap next to the top plate with a flashlight, and see down 8'.  The FG above the gap is stained black in a line due to filtering the air flowing up from the gap, and I have snow melt on the roof in patches over interior walls.  I could also see lines of warmth on the top (!) of the FG over the top plates with my IR thermo.  Just caulking my top plates dropped my BTU energy consumption by ~15% with no other changes to my house, as determined by logging run hours per degree day before and after.

IOW, its yuuuge.

More....

The 3/16" gap times the 200' linear gap length works out to a three square feet of opening between those cavities and my attic. The 15 wire penetrations are maybe 0.5 square inches each, or one tenth of a square foot.  IOW, the plate gap is 30x bigger area than the wire penetrations.


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## cableman (Apr 5, 2016)

I wish i took pics of my top plates, totally agree woodgeek. I wont have a sealed house as if i was building it now, but ill try my best to great stuff the hell out of every gap!


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## Seasoned Oak (Apr 5, 2016)

woodgeek said:


> Drywallers are taught to leave a 1/8 to 1/4" gap between the drywall and plate.
> 
> .


Whats the purpose for the gap? Expansion???  I always drywall right to the sidewalls ,so the wall sheets can support the top sheets. Iv never had a problem.  Usually blow cellulose in tight ,about 3-5 lbs pressurized to prevent settling. Although iv already pushed the drywall away from the wall if i dont have enough screws in yet ,with a good machine. Provides the best wall insulation at the lowest cost. THese new lightweight sheets are so nice! and stronger too.


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## woodgeek (Apr 6, 2016)

That was the way they did it in PA in 1960.  I figure it was expansion, but who knows?

Agreed on cellulose.  I am thinking of redoing my house exterior, currently 56 yo asbestos concrete shingles, and densepacking the walls at the same time.  I **think** they are mostly 1" thick R-3 FG 'econobatts' and several bays are just empty.


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## maple1 (Apr 6, 2016)

woodgeek said:


> Let's be empirical....
> 
> When I am in my attic, I can look into the gap next to the top plate with a flashlight, and see down 8'.



I'm having a hard time visualizing this. When you are looking down 8', what are you looking at? Are you seeing into the wall cavity? Or into the room below? I can't see how either is possible if the wall gyproc is pushed up against the ceiling gyproc and the joint is taped & mudded. I must be missing something. There is nothing to see there in my attic. The wall & ceiling framing were vapour barriered first, then ceiling & walls gyproced, then the joints taped & mudded.


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## cableman (Apr 6, 2016)

On mine the wall rock was not tight against the top plate so i can shine a light and look into my interior walls. Helped while snaking some wires!


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## Seasoned Oak (Apr 6, 2016)

woodgeek said:


> That was the way they did it in PA in 1960.  I figure it was expansion, but who knows?
> 
> Agreed on cellulose.  I am thinking of redoing my house exterior, currently 56 yo asbestos concrete shingles, and densepacking the walls at the same time.  I **think** they are mostly 1" thick R-3 FG 'econobatts' and several bays are just empty.


I just tore out a freezing bathroom that was 3.5 in FG batts in exterior walls. Completely useless! You could feel the breeze coming around the FG. Looked like it shrank too. 
Blew the walls tight with cellolose and the ceiling ,now the only heat i need in there regardless of the outside temps, is the infrared bulb fixture i installed in the ceiling,500 watts of drying and heating power. We like it in the 80s while showering.


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## Highbeam (Apr 6, 2016)

cableman said:


> On mine the wall rock was not tight against the top plate so i can shine a light and look into my interior walls. Helped while snaking some wires!



Odd but I believe you. Now how did this happen? When you install the wall rock you are setting fasteners into the top plate and the sheetrock is pulled tight to the top plate. Then, you mud and tape the joint. The only way that this gap could happen is if the top plate shrank and the mud/tape joint was so good that the wall rock stuck better to the ceiling rock than it did to the top plate. The fasteners were either pulled out if nails or they ripped through the rock.

None of my top plates have a gap to the wall rock. Maybe our lumber is better. Well, I can no better say that none of mine are gapped than you can say that all of yours are gapped but I can say that wherever I've looked, it's tight.

I agree that if you have this freak problem that you need to fix it.


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## cableman (Apr 6, 2016)

I would say they prolly never nailed to the top plate and it prolly shrank too. Some of the walls have 22.5 angles, u should have seen those gaps! It was actually blowing air on me when i pulled insulation up! I still have a location where i moved a thermastat and need to repair the sheet rock, not one bit of draft through it anymore. I was able to seal up both peak side exterior walls also. That great stuff pro gun is the best! 6 weeks i was in and out of my attics playing twister


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## blades (Apr 6, 2016)

I hate attic work , low attic here, unfortunately I am not particularly small therefore a lousy fit that leaves me feeling like I just got run over by a slow freight. Dreading the repairs I need to do up there - couple quotes were in the $2500 class expense, of which I am about 2300 short. Got to get the code work done at least, the rest will have to wait.


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## sesmith (Apr 6, 2016)

To the OP, you already have 12" of fiberglass so you're close to the recommended R38.  It might be a good idea to have an energy audit done with a blower door test to see what might be gained by additional air sealing.  

If it were me, I'd do the best I could myself to spot seal any places I could get to in the attic.  Then I'd put down additional insulation by blowing in cellulose on top of the fiberglass.  Why??  It's cheap.  I could do it myself with a big box store rental blower.  Cellulose permits much less air flow through it than fiberglass.  Then, I'd go down into the cellar and seal the rim joints myself.  This is easily done with cut and pieced in XPS sealed in place with spray foam in a can.  Pretty cheap and easy to do and little a bit messy. 

Then you'd have lots of money left to help with the wood stove install.  The stove will likely save you way more propane usage than insulation and air sealing will (unless a blower door test shows otherwise).


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