The issue is I don't believe anything from the reflectix site is correct. I think it is a R-1.5 insulation product. It radiation shield properties will deteriorate as soon as it gets dirty/dusty. And I think it is flammable. And priced at about 500% the cost to manufacture.
Air sealing success stories
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The issue is I don't believe anything from the reflectix site is correct. I think it is a R-1.5 insulation product. It radiation shield properties will deteriorate as soon as it gets dirty/dusty. And I think it is flammable. And priced at about 500% the cost to manufacture.
I went the spray foam route because it didn't cost much more. But if you don't want finished walls then why not consider Dow THERMAX foam board sheething? http://building.dow.com/na/en/products/insulation/thermaxsheathing.htm . It's supposed to be approved to be left exposed to the interior, but you should check with your local building dept. to be sure.
I didn't know there was a foam that didn't need to be covered. I'm going to have to look for a close distributor.
Or there is a spray foam company near you that offers "Intumescent Coatings: Includes thermal and ignition barriers to add a fire rating to your spray foam insulation as required by most codes".
http://www.upstatesprayfoam.com/energy-star.cfm
http://www.upstatesprayfoam.com/energy-star.cfm
This is what I was looking at. I think you can just glue it to the poured wall, and then you are done. I'm assuming the reflective surface enhances the R.
Does anyone know which of the rigid foams you can use with ground contact on the outside? I was thinking about trenching along the exterior to 36" and sliding rigid foam against the poured wall.
Yes, for the most part, the spray foam covers the sill plate and runs down the wall. We have some pipes and such running along the basement ceiling so it was probably a little difficult to work around given the pressure coming out of the wand. We took a pretty favorable loan through Efficiency Maine and will get about 15% back in rebates. I've seen somewhere that NH also offers some pretty decent rebates (better than Maine to my chagrin). Not sure if it was www.nhsaves.com, but I'm sure any home energy auditor would know what's available.
newbieinCT
Feeling the Heat
Thanks, woodgeek! Initial look at geothermal made it look amazing - the cold weather here will make it an issue in winter months. My dad loves learning about this stuff - the nerd in him comes out. He's been sending me links and texting me stuff that says the same was what you are. A combo is going to be the best for us. for now, we are investing in a good pellet stove. Next up, figure out a plan that will probably include wood insert (or possibly freestanding, not sure if there's room) and ductless. Going to have to speak with the neighbor that says he has geothermal. He has an old antique and I can't imagine it's all that warm...especially dead of winter unless he's eating up his oil (which terrifies me!)
Thanks for the advice
Geo is nice technology, and can provide cheap heat and a long service life. It's just very expensive up front, and many performance specs (that look awesome on paper) neglect the energy costs associated with pumping water in the ground loop. A good installer picks a right sized pump and the performance is great. A bad installer puts in a bad loop and an oversized pump, and the resulting system is an energy pig. It varies a lot.
For financial estimating, use our site's calculator: https://www.hearth.com/econtent/index.php/articles/fuel_cost_comparison_calculator/
with your local fuel costs. For the minis, put in 250% for efficiency in electric.
For financial estimating, use our site's calculator: https://www.hearth.com/econtent/index.php/articles/fuel_cost_comparison_calculator/
with your local fuel costs. For the minis, put in 250% for efficiency in electric.
Getting back to air sealing...I am, by nature, curious and I want to know how "tight" my house is and whether I should pursue more air-sealing measures. I want to stop short of adding a ventilation system (I don't want to make it too tight) due to cost and the fact that I have hydronic heat, so adding extra ventilation would be somewhat problematic and expensive. Here is the short summary (detail below) - I've tightened up a lot and achieved good results (the blower-door test guy was amazed at what I've achieved in my old house), but I still have room to improve (if I want to). It's almost impossible to make an old house too tight without a gut rehab.
Details:
I knew my CFM50 (and therefore my ACH50) and I had been wondering what the best "conversion" from ACH50 to ACH natural (not pressurized) should be. I had heard from elsewhere that a divide by 10 was a pretty good number to use, and others here (Woodgeek, Dick, Gary) suggested numbers in the range of 12-20. I used Gary's adjustment calculator (seep previous post) and came up with 16.375.
I also found that this presentation link http://www.buildingscienceconsulting.com/presentations/documents/Expert 2013 - Ventilation_rev.pdf confirms this range of numbers. See page (not slide) 62 and look at the slide in the bottom right where it references a study of a home in Quebec City that compared the ACH50 to a gas tracer test reading at normal pressure. The ratio was 4.16 (ACH50) / .30 (average gas tracer reading), or about 14.
So, I am going to assume 15 for my conversion from ACH50 to ACH(natural).
My original house blower door test was 1800 CFM at 50 Pa. I was told that if I sealed up the attic hatch better and the basement access door (which I subsequently did), I would probably drop to around 1200 CFM at 50 Pa, so I am going to use 1200 CFM as my "test" value. My house is 1250 square feet with a full basement, and 8.33 foot high ceilings in the living area and 7.5 foot height in the basement. So that gives me about 19,750 cubic feet. My ACH50 is (1200 cubic feet/minute * 60 minutes/hour) / 19,750 cubic feet = 3.65. My ACH(natural) would then be 3.65 / 15 (from above), or 0.24. I'm feeling pretty good about this, especially since my house is a 1922 bungalow, and I still really need to get into that attic and seal up a few hard to reach ceiling penetrations....Essentially, ACH50 of 3.0 is what you can get if you seal up the big holes and a 1.5 is possible addressing smaller holes (per the link above). I'm nearly there.
Now, I'd like to know "what is the lowest I could go without creating "problems" (health, odors, moisture, etc.) or without requiring mechanical ventilation. My "gut" tells me that I can push a little further...
Using my 0.24 ACH(natural), that would mean 86 CFM for the house, or doing the math (0.24 air changes/hour * 19,750 cubic feet) / (60 minutes/hour) = 79 cubic feet/minute of natural ventilation.
Referencing the above Joe Lstiburek presentation, the desired CFM for the house is 7.5 CFM per person + 0.01 to 0.03 CFM per square foot of conditioned living space. "Person" is defined as numbers of bedrooms + 1, which would mean 4 (even though my wife and I are the only occupants of the house). So that means 4 * 7.5 CFM + 0.01 * 1250 (square footage of living area) = 42.5 CFM (using the BSC formula) or 67.5 CFM (using the ASHRAE formula with a .03 multiplier). See pages 63 and 67 of the above referenced link for these formulas.
So it looks like that I am in the "safe" zone still on not making my house too tight. This is not surprising given that it is really, really hard to make an old house too tight unless you do a gut rehab (which there is no need to do on this house).
Next up...I need to motivate myself to rip up the attic floorboards and seal a few pesky ceiling penetrations, and also seal around the chimney chase. I can also make a few more improvements to the basement door sealing - realistically, I am probably not getting all the improvement I should since there are some areas I didn't seal at all and now that winter is here, I can feel the result of this.
Those planning to achieve the results I have should note that I have no appliances (excepting my wood stove) that utilize house air for combustion. Summary below:
Stove - electric
Range - electric
Water Heater - heat pump with electric backup
Boiler - oil using outside combustion air (though not "sealed combustion")
Woodstove - uses inside air for combustion drawn from the basement
I absolutely did not take the final steps to seal up the basement doors really well until I had a new boiler installed that used outside combustion air. I had previously noticed that if I was trying to establish a new fire and run the boiler at the same time, my woodstove chimney draft wasn't as good as it was with the old oil boiler not running. This raised concerns about sufficient ventilation to run these two appliances simultaneously. Now, there are no problems if I run both simultaneously.
Details:
I knew my CFM50 (and therefore my ACH50) and I had been wondering what the best "conversion" from ACH50 to ACH natural (not pressurized) should be. I had heard from elsewhere that a divide by 10 was a pretty good number to use, and others here (Woodgeek, Dick, Gary) suggested numbers in the range of 12-20. I used Gary's adjustment calculator (seep previous post) and came up with 16.375.
I also found that this presentation link http://www.buildingscienceconsulting.com/presentations/documents/Expert 2013 - Ventilation_rev.pdf confirms this range of numbers. See page (not slide) 62 and look at the slide in the bottom right where it references a study of a home in Quebec City that compared the ACH50 to a gas tracer test reading at normal pressure. The ratio was 4.16 (ACH50) / .30 (average gas tracer reading), or about 14.
So, I am going to assume 15 for my conversion from ACH50 to ACH(natural).
My original house blower door test was 1800 CFM at 50 Pa. I was told that if I sealed up the attic hatch better and the basement access door (which I subsequently did), I would probably drop to around 1200 CFM at 50 Pa, so I am going to use 1200 CFM as my "test" value. My house is 1250 square feet with a full basement, and 8.33 foot high ceilings in the living area and 7.5 foot height in the basement. So that gives me about 19,750 cubic feet. My ACH50 is (1200 cubic feet/minute * 60 minutes/hour) / 19,750 cubic feet = 3.65. My ACH(natural) would then be 3.65 / 15 (from above), or 0.24. I'm feeling pretty good about this, especially since my house is a 1922 bungalow, and I still really need to get into that attic and seal up a few hard to reach ceiling penetrations....Essentially, ACH50 of 3.0 is what you can get if you seal up the big holes and a 1.5 is possible addressing smaller holes (per the link above). I'm nearly there.
Now, I'd like to know "what is the lowest I could go without creating "problems" (health, odors, moisture, etc.) or without requiring mechanical ventilation. My "gut" tells me that I can push a little further...
Using my 0.24 ACH(natural), that would mean 86 CFM for the house, or doing the math (0.24 air changes/hour * 19,750 cubic feet) / (60 minutes/hour) = 79 cubic feet/minute of natural ventilation.
Referencing the above Joe Lstiburek presentation, the desired CFM for the house is 7.5 CFM per person + 0.01 to 0.03 CFM per square foot of conditioned living space. "Person" is defined as numbers of bedrooms + 1, which would mean 4 (even though my wife and I are the only occupants of the house). So that means 4 * 7.5 CFM + 0.01 * 1250 (square footage of living area) = 42.5 CFM (using the BSC formula) or 67.5 CFM (using the ASHRAE formula with a .03 multiplier). See pages 63 and 67 of the above referenced link for these formulas.
So it looks like that I am in the "safe" zone still on not making my house too tight. This is not surprising given that it is really, really hard to make an old house too tight unless you do a gut rehab (which there is no need to do on this house).
Next up...I need to motivate myself to rip up the attic floorboards and seal a few pesky ceiling penetrations, and also seal around the chimney chase. I can also make a few more improvements to the basement door sealing - realistically, I am probably not getting all the improvement I should since there are some areas I didn't seal at all and now that winter is here, I can feel the result of this.
Those planning to achieve the results I have should note that I have no appliances (excepting my wood stove) that utilize house air for combustion. Summary below:
Stove - electric
Range - electric
Water Heater - heat pump with electric backup
Boiler - oil using outside combustion air (though not "sealed combustion")
Woodstove - uses inside air for combustion drawn from the basement
I absolutely did not take the final steps to seal up the basement doors really well until I had a new boiler installed that used outside combustion air. I had previously noticed that if I was trying to establish a new fire and run the boiler at the same time, my woodstove chimney draft wasn't as good as it was with the old oil boiler not running. This raised concerns about sufficient ventilation to run these two appliances simultaneously. Now, there are no problems if I run both simultaneously.
Ok DBoon, I previously had a similar goal...to airseal my house to the point of min adequate natural ventilation, but not beyond, because adding an HRV would not be cost effective.
I agree with all your math above, but in the end I have come to a different conclusion. The issues are subtle, IAQ, humidity, freshness, allergens, performance in mild weather versus cold weather, etc.
The formulae you provided from ASHRAE and building science guru Joe L. are for determining proper mechanical ventilation rates in very tight houses. AFAIK, none of these guys recommend simply tightening a house such that ACH50/15 provides that rate. Instead they say that you should build tight ACH50 <3 and put in forced ventilation....an HRV in cold climates or either an HRV or a simple blower in mild climates. And the ventilation should have a controller the occupants can use to turn off the ventilation when it is not needed.
As I understand it, Joe L. and other gurus say that occupants in houses without mechanical ventilation start to give 'stale air' reports sometimes around or below ACH50 = 5. Reports of excessive winter humidity also start in around or below that level (depending on amount of water vapor sources, use of bath fans, etc). The ballpark value for 'lowest ACH50 that doesn't require some mechanical ventilation' is around 5, and that assumes the proper use of bath fans to control odors/humidity and cracking a window for fresh air during mild weather.
This ACH50=5 completely jibes with my experience. I started at ~ACH50 = 15+ (estimated) years ago and got down to a measured ACH50 = 5.5 this summer. Since more leaks were sealed after that work, I guess that I am around ACH50 = 4.5 now, with 4 occupants in 2250 square feet, and no combustion appliances. We have plenty of fresh air except when the outside temp is hovering in 55-75° range for extended periods. Specifically, under those conditions the house retains cooking odors >8 hours, and odors from tiny amounts of garbage can permeate the whole house at a low level. Running 1 bath fan continuously (80 cfm), or cracking a couple windows removes the problem completely. In the spring and fall, we do the window thing. In mild weather in the winter (as now) I switch the fan on. Not really a big hardship. Note that since I am only adding ventilation in mild weather, there is minimal energy penalty. ACH50 = 5 does not need extra ventilation in cold weather.
As for humidity, so far this year my humidifier has stayed in the closet and RH has ranged from 30-40%, even through some respectable cold spells. I intentionally don't vent shower humidity in cold weather; but if the RH got too high, I would.
So right now I have manual control of ventilation that is not a hardship, but if I miss it, as in the recent warm weather I come home to a smelly house and an annoyed wife. I am thinking of installing a single small blower on an outdoor thermostat to turn on when the outdoor temp is >50°F. That would be the budget alternative. Or I could just get a cheap HRV and run it more to get even fresher filtered air. I wouldn't duct it everywhere, just to my biggest space, and let the HVAC circulate it. The more time goes by, the more I am leaning to the second choice.
I agree with all your math above, but in the end I have come to a different conclusion. The issues are subtle, IAQ, humidity, freshness, allergens, performance in mild weather versus cold weather, etc.
The formulae you provided from ASHRAE and building science guru Joe L. are for determining proper mechanical ventilation rates in very tight houses. AFAIK, none of these guys recommend simply tightening a house such that ACH50/15 provides that rate. Instead they say that you should build tight ACH50 <3 and put in forced ventilation....an HRV in cold climates or either an HRV or a simple blower in mild climates. And the ventilation should have a controller the occupants can use to turn off the ventilation when it is not needed.
As I understand it, Joe L. and other gurus say that occupants in houses without mechanical ventilation start to give 'stale air' reports sometimes around or below ACH50 = 5. Reports of excessive winter humidity also start in around or below that level (depending on amount of water vapor sources, use of bath fans, etc). The ballpark value for 'lowest ACH50 that doesn't require some mechanical ventilation' is around 5, and that assumes the proper use of bath fans to control odors/humidity and cracking a window for fresh air during mild weather.
This ACH50=5 completely jibes with my experience. I started at ~ACH50 = 15+ (estimated) years ago and got down to a measured ACH50 = 5.5 this summer. Since more leaks were sealed after that work, I guess that I am around ACH50 = 4.5 now, with 4 occupants in 2250 square feet, and no combustion appliances. We have plenty of fresh air except when the outside temp is hovering in 55-75° range for extended periods. Specifically, under those conditions the house retains cooking odors >8 hours, and odors from tiny amounts of garbage can permeate the whole house at a low level. Running 1 bath fan continuously (80 cfm), or cracking a couple windows removes the problem completely. In the spring and fall, we do the window thing. In mild weather in the winter (as now) I switch the fan on. Not really a big hardship. Note that since I am only adding ventilation in mild weather, there is minimal energy penalty. ACH50 = 5 does not need extra ventilation in cold weather.
As for humidity, so far this year my humidifier has stayed in the closet and RH has ranged from 30-40%, even through some respectable cold spells. I intentionally don't vent shower humidity in cold weather; but if the RH got too high, I would.
So right now I have manual control of ventilation that is not a hardship, but if I miss it, as in the recent warm weather I come home to a smelly house and an annoyed wife. I am thinking of installing a single small blower on an outdoor thermostat to turn on when the outdoor temp is >50°F. That would be the budget alternative. Or I could just get a cheap HRV and run it more to get even fresher filtered air. I wouldn't duct it everywhere, just to my biggest space, and let the HVAC circulate it. The more time goes by, the more I am leaning to the second choice.
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lml999
Minister of Fire
27 years of marriage here...there's no better investment than my wife's comfort.
When she's happy, everybody is happy!
I certainly agree "happy wife = happy life". I also agree with the points that Woodgeek is making - as air infiltration goes down, other factors become more apparent. The folks at Building Science (Joe L. and friends) discuss this a lot.
I've been pretty cautious about how I've approached this for good reason - I don't want a moldy, smelly house that is a little more efficient on fuel, and I didn't want a tight house that fuel burning appliances couldn't function properly in. That was why I was explaining what I did and why, and where I was today. It's quite possible that if I did a new blower door test today, that I would not have reduced by CFM value (and hence my ACH50) to what I think I did - I could still be around ACH50 = 5.
I do think that I am reaching the law of diminishing returns anyways...which is why it is hard to motivate myself to do a lot of ugly, hard work to get a little bit more reduction. The reality is that I probably also once had an ACH50 = 15, and could feel drafts in the house. Now I don't and my wife and I are comfortable. So further motivation is tough, though I think I will still do a better job of sealing that basement door...
The next house will be sealed better upon renovation, and will have an ERV/HRV for sure. That is already dialed in to the plans.
I've been pretty cautious about how I've approached this for good reason - I don't want a moldy, smelly house that is a little more efficient on fuel, and I didn't want a tight house that fuel burning appliances couldn't function properly in. That was why I was explaining what I did and why, and where I was today. It's quite possible that if I did a new blower door test today, that I would not have reduced by CFM value (and hence my ACH50) to what I think I did - I could still be around ACH50 = 5.
I do think that I am reaching the law of diminishing returns anyways...which is why it is hard to motivate myself to do a lot of ugly, hard work to get a little bit more reduction. The reality is that I probably also once had an ACH50 = 15, and could feel drafts in the house. Now I don't and my wife and I are comfortable. So further motivation is tough, though I think I will still do a better job of sealing that basement door...
The next house will be sealed better upon renovation, and will have an ERV/HRV for sure. That is already dialed in to the plans.
newbieinCT
Feeling the Heat
Since I am the "wife", I wish I could disagree with this part of the thread. But I can't. I know that I will obsess over something I feel doesn't "work right". I think that's why the husband gave me full reign to ask questions and figure out the right stove...happy me = less questioning later
DBoon, I guess a better way to explain this is that ACH50 is a measured number. And ACH_nat is not a number, it is a function of time, wind, outdoor temp, and even its seasonal time average is only statistically correlated with ACH50. I would not be surprised if your ACH50 was 3.65 (measured) and you do NOT have problems with getting fresh air, while I can be at ACH50 = 4.5 and have noticeable issues during mild weather. My location is very wind sheltered. My airsealing in the attic is complete, so a lot of the CFM50 might be in the sides of the house. IF your residual leaks are top and bottom, not sides, and you are more wind exposed, your average ACH_nat can still be above mine.
I think the emerging paradigm in building science is about homeowner control. Giving folks an airsealed house where they can turn on a fan, an HRV or open a window is giving them more control over air quality than they had in a leaky house where the leaks could not be turned off (with out of control allergens and dust in mild weather, and hard to humidify dry air in the winter).
I think the emerging paradigm in building science is about homeowner control. Giving folks an airsealed house where they can turn on a fan, an HRV or open a window is giving them more control over air quality than they had in a leaky house where the leaks could not be turned off (with out of control allergens and dust in mild weather, and hard to humidify dry air in the winter).
Given that any estimation of ACH(natural) from an ACH50 reading is just that - an estimation only, I could certainly believe that two houses with identical ACH50 would have different performances in real-world conditions. I read somewhere else (can't remember where) that another way to estimate ACH(natural) is to measure and plot ACH at different pressures and extrapolate down to natural conditions.
In any case, "calculating" an ACH(natural) number is just an exercise in curiosity. I have a feeling that I'll know when I seal too much - but I haven't reached that yet. And it is certainly the case that if you are building new, the general idea is to build it tight and introduce a controlled amount of ventilation, and not have the ventilation be an uncontrolled infiltration.
In any case, "calculating" an ACH(natural) number is just an exercise in curiosity. I have a feeling that I'll know when I seal too much - but I haven't reached that yet. And it is certainly the case that if you are building new, the general idea is to build it tight and introduce a controlled amount of ventilation, and not have the ventilation be an uncontrolled infiltration.
27 years of marriage here...there's no better investment than my wife's comfort.
When she's happy, everybody is happy!
That reminds me of a bumper stick I once saw that read "If mama aint happy, aint nobody happy!"
But the all time funniest bumper sticker I've ever seen had to be "Jesus loves you, everyone else thinks you're an a$$h*&e." Please note that this wasn't meant to offend anyone here. I just found it to be a damn funny bumper sticker.
People get offended too easily.
I'm going to try to get a little more sealing done today. On Wednesday evening we're scheduled for -13F.
I'm going to try to get a little more sealing done today. On Wednesday evening we're scheduled for -13F.
Those nuts in Time Square will be a little cold this year. I had one kneewall left that will filled with bins of babyclothes. There is only a small entrance to it, so I was dreading getting in to seal that. The wife and I pulled everything out of it and I got foam up. 1" thick boards for most of it and spray foam around the edges. I'm sealed to the floorboards. I will go back and tape it just to make sure of the seal and then fill it back up. I purchased vacuum bags at Harbor Freight so maybe it will be a little less of a mass of stuff in there.
The foil faced polyiso product our local box store carries is the GAF EnergyGuard.
It has a flame spread rating of less than 75 which would put it in Class B. I"m not sure what Class materials are required in what living areas. Page 159 here would seem to contain that info from the IRC. http://www2.iccsafe.org/states/newjersey/nj_building/PDFs/NJ_Bldg_Chapter8.pdf
The Life Safety Code (NFPA 101)[5] and Section 803.1 of the International Building Code limit finishes for interior walls and ceilings to materials in three classes (A, B, or C, with A being the lowest flame spread and C being the highest) and gives greater restrictions for certain rooms:
Class Flame Spread Index
A 0-25
B 26-75
C 76-200
Edit: I'm doing some insulating work in the basement and have some areas where it would be great to have only the foam without an additional flame barrier over it. I thought I'd pass on the info above as it seemed relevant. I've not been able to find the TherMax product that Woodgeek referred to nearby so I was looking for alternatives.
It has a flame spread rating of less than 75 which would put it in Class B. I"m not sure what Class materials are required in what living areas. Page 159 here would seem to contain that info from the IRC. http://www2.iccsafe.org/states/newjersey/nj_building/PDFs/NJ_Bldg_Chapter8.pdf
The Life Safety Code (NFPA 101)[5] and Section 803.1 of the International Building Code limit finishes for interior walls and ceilings to materials in three classes (A, B, or C, with A being the lowest flame spread and C being the highest) and gives greater restrictions for certain rooms:
Class Flame Spread Index
A 0-25
B 26-75
C 76-200
Edit: I'm doing some insulating work in the basement and have some areas where it would be great to have only the foam without an additional flame barrier over it. I thought I'd pass on the info above as it seemed relevant. I've not been able to find the TherMax product that Woodgeek referred to nearby so I was looking for alternatives.
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The foam I'm using has to be separated from living areas by at least drywall. My drywall doesn't immediately cover it, but between the foam and the room is a framed knee wall.
I trimmed out the finished attic in the past 2 weeks and this is the first cold snap we've had since then. Part of what I did was to pull the caulk and such from around the windows and make sure I've foamed as much as I can and then recaulked and trimmed it out. The windows were installed before I was worried about things such as air sealing. Last night we got down to -6 and the house was snapping and popping from the cold. I don't recall that happening when we were down to -12 before. Maybe I caught a few small leaks doing it.
Matt
Matt
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