Net zero retrofit, something close to it or not?

[EbS-P]

I posed this question really hoping some had heard of an easy to tool help make the decisions. I don’t think a blower door test is a requirement that makes sense. We live in a world of big data that can be aggregated and then individualized.

Turns out the tool exist. Not for consumers mind you and not ready for nation/world wide deployment. Snug home pro and radiant labs.co are what you want to search for.

Here is the pod cast where I found out.

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

Like many things I’m ahead of the curve (as you are probably too if you’ve read this far).

 

[woodgeek]

Huh. Since stack and wind driven leakage is a major source of heat loss and latent loads for AC in homes, and a major uncontrolled/addressable source, it needs to be quantified.

Pros seem to think that a blower door test to 50 Pa gives a reliable measure of that loss term, and is cheap and quick to perform.

How do we estimate your house's ACH50 from aggregating and individualizing big data?

Story time:
I wanted to estimate my ACH_natural, but before I had a blower door test. I measured my indoor humidity (RH) with and without a humidifier running in winter. I did a ABABA measurement. And then crunched the numbers and psychometrics to get ACH_nat at that outdoor temp. I then worked the blower door correlation (ACH50 to ACH_nat) backwards to predict my blower door ACH50.

When the tech showed up for my 'before' ACH50 measurement I asked him what he thought I would get (I forget the number now). He said, 'Y' guessing from the age of construction. I said, uh, I think it will be X (2/3rd of his estimate). He measured it, I was bang on.

The next guy to come and measure the ACH50 'after' airsealing wanted to meet me... the airsealing guys had talked about me.

Just wanted to say that there are other ways of estimating ACH_nat!

 

[EbS-P]

Huh. Since stack and wind driven leakage is a major source of heat loss and latent loads for AC in homes, and a major uncontrolled/addressable source, it needs to be quantified.

Pros seem to think that a blower door test to 50 Pa gives a reliable measure of that loss term, and is cheap and quick to perform.

How do we estimate your house's ACH50 from aggregating and individualizing big data?

Story time:
I wanted to estimate my ACH_natural, but before I had a blower door test. I measured my indoor humidity (RH) with and without a humidifier running in winter. I did a ABABA measurement. And then crunched the numbers and psychometrics to get ACH_nat at that outdoor temp. I then worked the blower door correlation (ACH50 to ACH_nat) backwards to predict my blower door ACH50.

When the tech showed up for my 'before' ACH50 measurement I asked him what he thought I would get (I forget the number now). He said, 'Y' guessing from the age of construction. I said, uh, I think it will be X (2/3rd of his estimate). He measured it, I was bang on.

The next guy to come and measure the ACH50 'after' airsealing wanted to meet me... the airsealing guys had talked about me.

Just wanted to say that there are other ways of estimating ACH_nat!

Large scale it’s not practical to blower door test every single home.

We know location, square footage, footprint, date of construction any permits that were pulled. In a perfect world we would know utility consumption. Now I am guessing here, but you probably do have an energy model of a similar home in similar location.

An energy consultant /building advisor shows up on site with all this data and in 30 minutes or less. Has a good enough full energy profile and is able to run the cost benefit analysis of your upgrade options that meet your budget. That’s how they were selling it on the podcast. Selling the product at scale (think New York State) makes them the most profit.

They don’t have to be perfect. They know old ducts leak. Lots of unsealed recessed lights leak. You get the point. If they see big holes in the quick walk through they can adjust.
Granted they really don’t care if your hvac equipment sizing is correct.

But it is answering my question, true net zero isn’t really is not a standard that we need proof of. Close as one budget takes you is good enough. And the energy models guide that process.

 

[stoveliker]

I disagree. Zero is zero. Net or otherwise. To reach zero, you gotta measure the specific case.

That software is nice. It is helpful in reducing energy consumption. But it has nothing to do with net zero, other than that the definition of reduction is "getting closer to zero".

 

[EbS-P]

I disagree. Zero is zero. Net or otherwise. To reach zero, you gotta measure the specific case.

That software is nice. It is helpful in reducing energy consumption. But it has nothing to do with net zero, other than that the definition of reduction is "getting closer to zero".

But I argue that it’s not cost effective to quantify every home. If we want to get to net zero (or make xx% improvement to net zero) we will use models and estimates. It’s not that zero is a magic number where all problems are solved. The next goal is carbon capture so we need to do better than net zero and have an energy surplus.

I totally think some leader/policy maker will make a proud announcement (“we have achieved ______xyz_”) based on software and models and most will take that as fact.

 

[stoveliker]

I agree with you that (over the whole of society) it's better to invest in getting everyone 90 pct down than the much larger investment of getting a few to actually zero.

My remark was that if you're not aiming for zero, don't call it that. Just call it making your home more efficient. If you want a bet zero home, you are proclaiming a numerical value - and then you have to show that it is the right numerical value. Otherwise "net zero" looses all its meaning.

 

[woodgeek]

The gaps in construction are not consistent. Some buildres left large gaps, some left small.

A blower door is a cheap tool, and taking the measurement takes 5 minutes. They could have them at the library, and you could borrow them for free. Not sure why you are so down on them.

It's easier (and more informative/quantitative) than FLIR.

 

[woodgeek]

Getting to your point, one measure that is pretty useful is just to turn off your heat and measure how fast the indoor temperature falls (°F/hr) at a given outdoor temp. This rate is proportional to the shell thermal conductivity (U factor) divided by the heat capacity of the mass inside the envelope. The first term is closely related to that pesky BTU/HDD.sqft figure (if we assume the thermal mass is also proportional to sq ft).

I measured that rate during my retrofits, and as expected it fell by a factor of about 2. You need to let the house cool for a long time and decent Delta T to get a good reading. I would do this while the family was asleep, or traveling. 🥶

It can also be used to compare different houses with similar square footage to rate them for energy efficiency (so long as they don't have some huge variation in thermal mass). IIRC, the largest source of thermal mass in conventional construction is gypsum wallboard, BTW.

Ecobee estimates this rate of loss automagically for my house (during setback periods I think) and ranks me against other customer in the area, on a monthly average basis (they send me a report card). It says I am somewhat above average compared to my neighbors.

What Ecobee ALSO does is measure HVAC runtime as a duty cycle, and rate me on that metric as well. There it says I am terrible, but I assume it is comparing my heat pump running flat out at 25°F to folks running oversized gas and oil-fired equipment that can heat their house in a polar vortex with a 30-40% duty cycle. This is what many utilities (and my former Nest tstat) usually do. I ignore this metric.

So Ecobee (and Nest) like to claim that they CAN estimate U factors for existing houses. This info could be used to direct retrofitting funds in principle. IMO Ecobee has done a MUCH better job with this data analysis, and Nest has done a better job lining up utility partners. So the utilities have bad (Nest) data. Sigh.

 

[EbS-P]

The gaps in construction are not consistent. Some buildres left large gaps, some left small.

A blower door is a cheap tool, and taking the measurement takes 5 minutes. They could have them at the library, and you could borrow them for free. Not sure why you are so down on them.

It's easier (and more informative/quantitative) than FLIR.

So for arguments let’s assume I don’t care about quantifying my energy consumption or the net zero label. I have done my best to seal everything I can think of that I can. I’m not pulling window trim. The attic got a case a caulk and spray frame and I moved all my loose fiberglass around to get what I would considered as good an any home owner who is diligent can do. Sealed and insulated all my rim joists. Any j box on an exterior wall has been foamed/caulked and gaskets installed. Any exterior penetration sealed as best I can.

What can I expect the blower door to reveal?

 

[woodgeek]

So for arguments let’s assume I don’t care about quantifying my energy consumption or the net zero label. I have done my best to seal everything I can think of that I can. I’m not pulling window trim. The attic got a case a caulk and spray frame and I moved all my loose fiberglass around to get what I would considered as good an any home owner who is diligent can do. Sealed and insulated all my rim joists. Any j box on an exterior wall has been foamed/caulked and gaskets installed. Any exterior penetration sealed as best I can.

What can I expect the blower door to reveal?

It will reveal if you somehow missed something worth hunting for, or if you got 'em all.

I would say that in a 'pro retrofit' job doing a before and after blower-door is more important, to make sure that the (invisible) job is being done to spec. Most incentive programs require it for this reason to keep everyone honest. My guys were worried that I had already done enough airsealing that they would have a hard(er) time meeting their mandated improvement threshold to qualify for state rebates (paid to me).... but they went the extra mile and made it.

For DIY, you have your own incentives to keep you honest/diligent.

Sounds like you did good. Can you see/feel a difference in your heating /cooling?

 

[EbS-P]

It will reveal if you somehow missed something worth hunting for, or if you got 'em all.

I would say that in a 'pro retrofit' job doing a before and after blower-door is more important, to make sure that the (invisible) job is being done to spec. Most incentive programs require it for this reason to keep everyone honest. My guys were worried that I had already done enough airsealing that they would have a hard(er) time meeting their mandated improvement threshold to qualify for state rebates (paid to me).... but they went the extra mile and made it.

For DIY, you have your own incentives to keep you honest/diligent.

Sounds like you did good. Can you see/feel a difference in your heating /cooling?

I’m only two cans of spray foam in. My FMLA leave starts once finals are over in two weeks. So at this point it’s all still on my todo list. It’s nice that’s is a start and stop project. Baby #5, according to her bothers, “is a lot”. That’s probably an understatement……

 

[stoveliker]

I hope you (and your wife) will have a good FMLA leave. I remember having projects lined up - and not getting to them...
And that was with the second one only (not a 5th).

 

[begreen]

I did most of our sealing projects incrementally until 2006 which was a major renovation. It's a real challenge as the kids are growing up so I addressed the most blatant issues in the first couple of years after moving into this house. They were so obvious that they couldn't be ignored or delayed. During this process, I discovered a lot more issues that required planning and sometimes rejection of simpler alternatives that failed to meet the grade. Still, even after the major renovation, it is clear that this house will never meet net Zero, so we do the best we can and work on other areas. One place that we really have succeeded is waste reduction.

 

[stoveliker]

Yes, I discovered a lot of other issues too. Safety issues in electrical systems that would otherwise have remained out of view.
It's good to get into the nooks and crannies of your home.

 

[woodgeek]

As @begreen said... as you get into it, you will find more issues.

I have a split level, and it had some open framing bays into the attic, and poorly insulated side walls in the attic... that took a bit more effort to fix. I ended up retrofitting a HP airhandler and new ducts into the attic space, and the installer didn't seal the ducts (discovered later). So i had to tear down all the duct insulation, seal the ducts, and then re-insulate them! I couldn't reach the air gaps nearest the eaves, bc the space was too small for me to fit into... the pros came with their 'little guy' who specialized in that (!) and zapped them with spray foam on a wand. My rims are behind finish walls (!), and the pros dense-packed the cavities adjacent to the rims with a few drywall holes (that I could patch).

IOW, it was a much bigger job than I thought, and some of it I was happy/needed to pass to pros. But very satisfying to get a >50% reduction without any major remodeling, or popping window trim (or gasketing my outlets). And that on a house that LOOKED like it was OK... piles of insulation in the attic, storms on most windows, good weather stripping everywhere (the previous owners TRIED, but failed).

 

[EbS-P]

I had a conversation with an architect friend. Asked if anyone in the area is designing and building net zero or almost passive homes. He shook his head.
His response was.
“ 30 In overhangs2x6 walls with spray foam and cellulose. Don’t cut down all the trees.” He designed and built his house 4 years ago.
Edit*** this is the same guy who neglected a fresh air intake for his zero clearance fireplace and had to cut a hole in the floor to get fresh air in.

Says his electricity bill is 100$ a month. Mine with a 300 kWh of car charging will probably average 140$ Their one kid to our 5. Their brand new 2x6 with spray foam construction to our 1968. 2x4 with a bit of insulation. I’m doing ok.

 

[woodgeek]

Yeah, if you haven't already, you can read about the 'Pretty Good House' PGH.

A lot of the original content got paywalled.

There is a book: Amazon product ASIN 1641551658
The idea is that rather than going crazy to make something like a Passive House, you can do a few lower cost design changes/upgrades to conventional construction to dramatically reduce energy needs. And then do solar to get (or approach) Net Zero and excellent durability/resilience.

You ARE doing OK. Your HPWH and lack of dryer usage is probably a big part of the difference. Oh and most architects have a rather poor understanding of building science and performance, and tend to chase fads. I think that is why LEED is such a disappointment.

 

[stoveliker]

That was my point with e.g. attic sealing. That is the low hanging fruit that (to me), regardless of how good you already are, should be a "why not" improvement. Even if only for ROI reasons... (Which I use as the definition of low hanging fruit.)

I (1977 2*4 built) used an average of 10.5 kWh before my minisplit (no AC then). Oil + wood heat, oil hot water, electric cooking, variable speed pool pump, electric dryer. 1700 sqft 2x4, 2 adults, 10 and 12 y/o kids.

With minisplit (for AC and heat), I use 15 kWh per day, averaged over the year. Using zero oil for heat (some for water). Wood + minisplit heat.

(I think that is a better comparison than price, at least on this forum rather than with the neighbors.)

Of course your electric base heating (heat pump) changes any comparison with others that have oil or nat gas.

Yes, you're doing quite okay imo.

 

[EbS-P]

Yeah, if you haven't already, you can read about the 'Pretty Good House' PGH.

A lot of the original content got paywalled.

There is a book: Amazon product ASIN 1641551658
The idea is that rather than going crazy to make something like a Passive House, you can do a few lower cost design changes/upgrades to conventional construction to dramatically reduce energy needs. And then do solar to get (or approach) Net Zero and excellent durability/resilience.

You ARE doing OK. Your HPWH and lack of dryer usage is probably a big part of the difference. Oh and most architects have a rather poor understanding of building science and performance, and tend to chase fads. I think that is why LEED is such a disappointment.

He’s a smart guy married to a really smart bio PhD. And I asked how they were bringing fresh air in. He said the hole he cut so he can burn his fireplace. Spray foamed the whole house and no fresh air ventilation. There will be a growing market for a building advisor role that can be the go between the architect, HC, hvac, plumber, electrician etc. was floored we can get by with a 3 ton unit.

 

[EbS-P]

That was my point with e.g. attic sealing.

I (1977 2*4 built) used an average of 10.5 kWh before my minisplit (no AC then). Oil + wood heat, oil hot water, electric cooking, variable speed pool pump, electric dryer. 1700 sqft 2x4, 2 adults, 10 and 12 y/o kids.

With minisplit (for AC and heat), I use 15 kWh per day, averaged over the year. Using zero oil for heat (some for water).

(I think that is a better comparison than price, at least on this forum rather than with the neighbors.)

Of course your electric base heating (het pump) changed any comparison.

Totally better to use consumption over cost. But he didn’t know his consumption. And my guess 100$ was what it was 3 years ago when he cared.

 

[mcdougy]

Do a blower door test, Blow more insulation in your attic, and fix your crawl space by conditioning the space. Then you have a chance at a home that's performing well. IME.

 

[peakbagger]

Nh has a pretty good home energy reduction project for retrofitting existing housing stock. The homeowner pays for the initial audit including a blower door test and then the auditor working with contractor come ups with a best bang for the buck estimate. The utility will pay for up to $6000 of improvements as long as certain cost benefit ratio is obtained. The work is then done and there is post test audit including the blower door. The contractor does not get paid unless the meet the estimates. The utility has their own auditor and picks a random sample of homes to do their own post audit. A typical home energy audit takes 4 hours and is valued at $600. The cost of the audit is covered by the utility if the homeowner had work done.

I went to seminar a few days ago where the state is begging contractors to go into the business of doing audits and the subsequent sealing and insulation services. The contractor running the seminar claims he has 5 foam crews, 7 cellulose crews and 5 auditors. He has a two month backlog. He said that on the vast majority of projects they dont even touch the walls and windows. Attic sealing including hatches and additional insulation eats up most of the $6,000 with the basement sills and general sealing of air leaks eats up the rest. Payback on windows rarely meets the threshold unless they are older homes with sash weights and pockets.

He uses a thermal camera but its pretty rare that they will actually go after insulation issues in walls as the money is already spent elsewhere. The goal is not net zero for sure but its doing long term fixes that may have less than a 2 year payback.

I picked up a FLIR E8 high resolution Thermal Camera for work but with my retirement, its mine to do with what I wish. I plan to be using it around the house in lot of places.

 

[EbS-P]

Nh had pretty home energy reduction project for retrofitting existing housing stock. The homeowner pays for the initial audit including a blower door test and then the auditor working with contractor come ups with a best bang for the buck estimate. The utility will pay for up to $6000 of improvements as long as certain cost benefit ratio is obtained. The work is then done and there is post test audit including the blower door. The contractor does not get paid unless the meet the estimates. The utility has their own auditor and picks a random sample of home to do their own audit. A typical home energy audit takes 4 hours and is valued at $600. The cost of the audit is covered by the utility if the homeowner had work done.

I went to seminar a few days ago where the state is begging contractors to go into the business of supply audits and the subsequent sealing and insulation services. The contractor running the seminar claims he has 5 foam crews, 7 cellulose crews and 5 auditors. He has a two month backlog. He said that on the vast majority of projects they dont even touch the walls and windows. Attic sealing including hatches and additional insulation eats up most of the $6,000 with the basement sills and general sealing of air leaks eats up the rest. Payback on windows rarely meets the threshold unless they are older homes with sash weights and pockets.

He uses a thermal camera but it pretty rare that they will actually go after insulation issues in walls as the money is already spent elsewhere. The goal is not net zero for sure but its doing long term fixes that may have less than a 2 year payback.

I picked up a FLIR E8 high resolution Thermal Camera for work but with my retirement, its mine to do with what I wish. I plan to be using it around the house in lot of places.

I really wish we had a forward thinking legislature. They outlawed any long term planning that included sea level rise. I think that’s been changed but was in force for 4-5 years.

Payback down here is really long. Last time I signed up for the utility sponsored energy audit it was a 70 degree day and 70 inside and the guy walk around with his thermal camera left me box of out let seals and low flow faucet screens and a shower head. It was a waist of time.

 

[mcdougy]

These programs have been happening for the last decade off and on here . The test and incentives are almost identical as what's been mentioned. R 60 attics and basement/crawlspace work is best value but if your doing a large renovation there is some upside with windows,doors, appliances etc.
The latest programs are focusing on heat pump installs if your replacing a oil furnace.The East Coast is really encouraging people to make a switch in heating.