Net zero retrofit, something close to it or not?

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EbS-P

Minister of Fire
Jan 19, 2019
3,543
SE North Carolina
I’m an energy conscious person. None of the work we have done to our home was done to achieve a net zero home. We put in a wood stove. Then a HPWH. New windows ( not great ones).

Now I am learning more and really want to tighten up my envelope, add insulation , encapsulate the crawl space, and replace all the duct work I am examining what step one should take if they wanted to retrofit and existing home to be a net zero home.

The whole process is is highly data driven and really needs informed contractors. Both things I am lacking. So the topic for discussion is….

Is a net zero retrofit really necessary or is as good as a well informed, thoughtful homeowner with smart phone good enough?
Any there any expensive mistakes one might make taking this DIY data-less approach?

How important is a manual j? How much experience is really needed to do a net zero heating cooling ventilation design and install. Can you do it without a blower door test?

My current thinking is do the best I can (and can reasonably afford ( new hvac equipment is not in budget now)) and see where I end up. Add solar in a couple years if it still a good decision nothing can be net zero without it.

Any/all thoughts are appreciated

Evan
 

woodgeek

Minister of Fire
Jan 27, 2008
4,780
SE PA
I did a ton of retrofits on my 1960 house starting after I moved in 2008 until about 2013. A mix of major and minor DIY and finally a round of pro work.

IMO, the major factor is BTU/day.ft^2.°F. How much heat do you leak BTU per heating degree day per square foot? Take your BTU input over a season in BTUs, and divide it by your conditioned sq footage and HDD for that season (adjust for actual thermostat setting).

My house was (IIRC) about 10 on that scale, which is a dog (lower is better), but pretty typical of 1960 construction that has not been airsealed. Now keep in mind when I moved in that the windows had storms, and the doors and windows were weatherstripped and the attic had a bunch of insulation in it. But it was still a 10.

For comparison, one definition of a passive house is a '1' on that scale, which would require a 90% reduction of heat loss. Wow.

Another definition is the 'pretty good house' which is more like 2 or 3, and a pile of solar panels on it to be net zero.

After all my work (maybe 200 hours DIY and $5k pro airsealing, and $5k for new low-E storm windows and R-30 attic blow in) I dropped my heat loss in half, to 5. I got more than half that improvement from DIY.

My ecobee tells me my heat loss is better than the median for my area (mostly newer construction). :)

In order of importance:
1. Attic airsealing
2. Rim joist airsealing
3. Attic insulation to R-30
4. Low-E storms

Right now my walkout basement still has uninsulated walls (pros wouldn't blow into a cavity on or below grade). If I got those cavities filled, I might drop to 4 or 4.5.

Everything else is in the noise. Getting deeper (than a 60% reduction) would be super expensive and pointless TBH (would require heavy work on exterior, like wrap and foam, and replacing all the doors, and maybe the windows).

I would say that there is a point of diminishing returns on retrofit. There are a lot of low hanging fruit (not windows and doors generally). Airsealing is stupid good payback. Insulation is decent. Beyond that it gets sketchy on payback (like >10 years), esp in your milder climate.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,780
SE PA
To address your questions... IMO converting an existing home into a 'zero energy' home is very difficult and/or expensive and rarely done (making it unlikely you will find a skilled contractor to do it).

That said, you CAN get an intensive energy audit and proposal for energy savings retrofits. Usually the auditor will be a separate outfit from the contractor (but they can provide references) to avoid COI. The auditor report will be data driven based upon a multi-hour inspection of your home with thermography and a blower door test and a walk/crawl through. Proposed retrofits will be sorted according to their cost and simple payback time. You can then move forward with whatever projects you want.

Often these can net 50% in older construction with paybacks <10 years. In my case, they didn't get that much bc I had already nabbed a lot of the low hanging fruit.

But after that improvement, your house will still probably use 2X as much energy as a net-zero home.
 
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EatenByLimestone

Super Moderator
Staff member
A homeowner can certainly hit the low hanging fruit by themselves.

Unfortunately the stuff that is then left is expensive and probably has a long payback.

The payback is the important thing imo. If I need to spend $10k to save $20/month during the winter I'm probably not going to do it unless I can be convinced itll improve my comfort.
 
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EbS-P

Minister of Fire
Jan 19, 2019
3,543
SE North Carolina
At this point I don’t see what an energy audit would get me and even if it did have a blower door test. a cold day/night light the stoves and turning the bathroom fans an look around with my IR camera is probably good enough.

I’m really thinking net zero is a marketing tool. Do what you can to seal and insulate an then add a much solar as you are comfortable paying for or space will allow.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,780
SE PA
Feh. Not sure why you are so down on a quality audit. There are MANY different things you can do to your house, and it is not clear where to start... what will have the best bang for the buck. The reality is that many homeowners think they can do this themselves, and then put a HUGE effort into weatherstripping their windows (bc they can feel the draft) or insulating their floors (bc the floor is cold) or blow a pile of insulation into an non-airsealed attic (which does little to nothing) or spend a bundle on reflectix attic insulation (which does nothing to an airsealed and insulated attic).

And it is all a big waste of time, money and energy in the end.

In the end, your house needs to be quantified, modeled and payback needs to be estimated. My windows are 62 years old, wood and single pane. I could've dropped $50k replacing them all, but instead got low-E storms (that I did not know existed) for a tenth that and get a U =0.3 factor!

I'm a (handy) scientist and spent a HUGE amount of time reading, measuring, calculating and modeling to be able to do what I did. 99% of DIY folks do this retrofitting stuff wrong. I will give you more credit than that, but I will say that it is REALLY counterintuitive, and your biggest losses are not what you think, see or feel, even with a FLIR.

The blower door quantifies how much leakage you have, before airsealing AND after. Airsealing with qualification is wishful thinking.

You can pay a pro to crunch all the numbers FOR YOU, and then you can do as uch or as little of the work as you like DIY, confortable in the knowledge that you are doing it right and efficiently. And getting a fair payback (or at least not wasting your time).

Net Zero is a buzz-word. A target for new construction. Get the house as tight as you can, and put as much solar on as you can (if you like). It won't be net zero, but it will be better than any other house on the block.

My efforts have reduced my household CO2 emissions by over a hundred tons over the last decade. You can do it too.
 
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EbS-P

Minister of Fire
Jan 19, 2019
3,543
SE North Carolina
Feh. Not sure why you are so down on a quality audit. There are MANY different things you can do to your house, and it is not clear where to start... what will have the best bang for the buck. The reality is that many homeowners think they can do this themselves, and then put a HUGE effort into weatherstripping their windows (bc they can feel the draft) or insulating their floors (bc the floor is cold) or blow a pile of insulation into an non-airsealed attic (which does little to nothing) or spend a bundle on reflectix attic insulation (which does nothing to an airsealed and insulated attic).

And it is all a big waste of time, money and energy in the end.

In the end, your house needs to be quantified, modeled and payback needs to be estimated. My windows are 62 years old, wood and single pane. I could've dropped $50k replacing them all, but instead got low-E storms (that I did not know existed) for a tenth that and get a U =0.3 factor!

I'm a (handy) scientist and spent a HUGE amount of time reading, measuring, calculating and modeling to be able to do what I did. 99% of DIY folks do this retrofitting stuff wrong. I will give you more credit than that, but I will say that it is REALLY counterintuitive, and your biggest losses are not what you think, see or feel, even with a FLIR.

The blower door quantifies how much leakage you have, before airsealing AND after. Airsealing with qualification is wishful thinking.

You can pay a pro to crunch all the numbers FOR YOU, and then you can do as uch or as little of the work as you like DIY, confortable in the knowledge that you are doing it right and efficiently. And getting a fair payback (or at least not wasting your time).

Net Zero is a buzz-word. A target for new construction. Get the house as tight as you can, and put as much solar on as you can (if you like). It won't be net zero, but it will be better than any other house on the block.

My efforts have reduced my household CO2 emissions by over a hundred tons over the last decade. You can do it too.
I think my real hesitation to get an audit is once I quantify everything the ROI for everything but solar is prohibitively long. And I’m not ready to cut down all the trees to put up a 6-8kw array. So Picking and spending on one project at a time without running the numbers feel like I’m more likely to get something done
 

woodgeek

Minister of Fire
Jan 27, 2008
4,780
SE PA
Hmmm. Airsealing work DIY has a payoff time measured in months. Blow in insulation, a couple years. Solar... you might find out that THAT has a lousy payback.

And Matt is right... there are benes other than money payback. The comfort factor in my house is huge, like getting a whole new house. The amount of dust and allergens, the gradient when I'm heating with the stove... a bunch of stuff.

You won't feel any of that from solar.
 

EatenByLimestone

Super Moderator
Staff member
I had my walls dense packed with cellulose. It did help with heating and cooling, but the biggest benefit was unexpected. The amount of road and neighbor noise it stopped was huge!
 
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EatenByLimestone

Super Moderator
Staff member
I wish I had known as much about spray foam as I do now. I would have found the money to foam my attic when I finished it off. I’d like to now, but if my electricity and gas is $100/month, gas being about $30, there isn’t much savings to realize.
 
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EbS-P

Minister of Fire
Jan 19, 2019
3,543
SE North Carolina
We just don’t have heating and cooling demand to make any real big insulation upgrades cost effective. Air sealing sure that going to get me huge improvements. Still working on it.

At this point one might want to consider EV charging into the net zero calculations. I’m guessing I will spend as much on charging as I do heating and cooling during the year. Roughly 300kwh a month.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,780
SE PA
So, to summarize, you want to (grudgingly) do some airsealing, not touch your insulation, then install a chit ton of solar and get a gold star for being net zero/green? But you'll have to cut down some trees to do that, so you're procrastinating? And worried that in the end, your Tesla will use more juice (combined with house) than your solar can provide, so you won't be 'green enough' (net zero)?

Sounds harsher than it is intended... but I am really not getting your motives.

If you are saving energy by any means, the first ton of CO2 you save has just as much impact as the tenth ton you save. When you compute that you have reached net zero (by some metric) its not like fireworks go off and some dude comes to your door and says 'Now you're good!' and then you can sleep well at night (or whatever).

IIRC you are more excited about getting solar (like its a magic bullet or something) than doing other things to reduce your emissions.

Even if you offset all your elec usage with solar panels, the panels still required some CO2 in their production, so you would only be reducing your CO2 impact by about 90%, and then only if you were 100% off-grid. With an annual net meter system, there are still emissions associated with using the 'grid battery'. The grid power you are using makes emissions, and when you are powering the grid, you are 'offsetting' emissions at that time. Is the CO2 intensity when you are offsetting the same as when you are drawing? And if there is a limit to how many customers can use the grid battery, aren't you just preventing someone else (perhaps the utility) from using the grid battery a few years hence, a zero sum game?

In reality, everything we do has an environmental and climate impact. Eliminating the elec usage up front is obviously way better than offsetting it with grid tie solar. Its just a lot less visible/sexy. My ex saw me doing all the work (and spending for pro work) on the house for years. She appreciated the comfort improvements, didn't care about the payback/savings, and was angry that the house looked exactly the same afterwards.... it was all invisible. Too bad.

I recently computed that the milk I was putting in my coffee and to wet my morning cereal required 0.3 acres of pasture land to produce. WOW. I found a nice full fat outmilk for my coffee, and 2% for my cereal, and am probably saving as much CO2 from that change as from burning a face cord of wood every season to offset my electricity.

I might want the wood burning to be greener, but just grabbing a different carton at the grocery store is as green as it gets.
 
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EbS-P

Minister of Fire
Jan 19, 2019
3,543
SE North Carolina
So, to summarize, you want to (grudgingly) do some airsealing, not touch your insulation, then install a chit ton of solar and get a gold star for being net zero/green? But you'll have to cut down some trees to do that, so you're procrastinating? And worried that in the end, your Tesla will use more juice (combined with house) than your solar can provide, so you won't be 'green enough' (net zero)?

Sounds harsher than it is intended... but I am really not getting your motives.

If you are saving energy by any means, the first ton of CO2 you save has just as much impact as the tenth ton you save. When you compute that you have reached net zero (by some metric) its not like fireworks go off and some dude comes to your door and says 'Now you're good!' and then you can sleep well at night (or whatever).

IIRC you are more excited about getting solar (like its a magic bullet or something) than doing other things to reduce your emissions.

Even if you offset all your elec usage with solar panels, the panels still required some CO2 in their production, so you would only be reducing your CO2 impact by about 90%, and then only if you were 100% off-grid. With an annual net meter system, there are still emissions associated with using the 'grid battery'. The grid power you are using makes emissions, and when you are powering the grid, you are 'offsetting' emissions at that time. Is the CO2 intensity when you are offsetting the same as when you are drawing? And if there is a limit to how many customers can use the grid battery, aren't you just preventing someone else (perhaps the utility) from using the grid battery a few years hence, a zero sum game?

In reality, everything we do has an environmental and climate impact. Eliminating the elec usage up front is obviously way better than offsetting it with grid tie solar. Its just a lot less visible/sexy. My ex saw me doing all the work (and spending for pro work) on the house for years. She appreciated the comfort improvements, didn't care about the payback/savings, and was angry that the house looked exactly the same afterwards.... it was all invisible. Too bad.

I recently computed that the milk I was putting in my coffee and to wet my morning cereal required 0.3 acres of pasture land to produce. WOW. I found a nice full fat outmilk for my coffee, and 2% for my cereal, and am probably saving as much CO2 from that change as from burning a face cord of wood every season to offset my electricity.

I might want the wood burning to be greener, but just grabbing a different carton at the grocery store is as green as it gets.
I really think we need more frank discussions and your harshness is on point and appropriate and appreciated. I think the whole net (near) zero, unless adopted into building code, is fringe concept only accessible to those who with well above average understanding and means.

As for motivation I do feel that I need to take some actions, to at the very least be an environmentally aware role model to my kids who are still being taught recycling is the answer in school, and that polar bears are eating their young but nothing about factual carbon emissions and how to reduce them.

I want to model responsible stewardship on a realistic middle/upper middle class income for young families. I don’t think we have enough of those discussions. But we sure are happy to talk about the latest score for some sport, that that gets huge tax breaks. How do we more people to care?

My wife gets it but could care less when it comes to her own actions. Taking the family on nice vacations she never got as a kid is way more important to her than any other decision.
 

woodgeek

Minister of Fire
Jan 27, 2008
4,780
SE PA
I get your conundrum. You can do things to ACTUALLY save energy/CO2 to your house, but if they are invisible, then there is no 'lesson' for your kids or modeling for your neighbors.

When I did my retrofits, I **told** my grade-school age kids that I was doing it to save energy and CO2, and that it was stupid not to do it, bc I could save money at the same time... win-win-win. They got it. When they learned more about the climate later, they already knew what side Dad was on, and where he put his own attention, sweat and dollars. They have always remain convinced of that about me.

I told my neighbors (with the same house by the same 1960 builder) about the huge savings from attic airsealing and they had it done. I can tell from the snow on our rooves that their job wasn't quite as good as mine, but its respectable. They are still heating with oil (unlike me who switched in 2008), but TBH, the heat pump tech was not that great until recently, and I haven't saved a lot of money (its a wash with equipment cost). So their choice is reasonable based on engineering and $$.

I told/shamed a different neighbor to switch to a heat pump (from propane) when he did a big expansion/remodel. He cries about the January electric bill, but he's happy the other 11 months.

When I got an EV in 2014, I got a LEAF on a $200/mo lease. As a family with small kids, we ended up carpooling kids in it. We let all the kids 'plug it in' which they were excited about (at 10 yo). Their parents asked, we told them it was CHEAP and did everything we needed a (second) car to do. Eventually we gave them extended test drives. Two families we knew got LEAFs in 2015. We modeled that. Both families stuck with the EVs ever since, getting a Gen 2 LEAF and Tesla model 3s.

Does your driving the Model X around convince anyone to drop $100k on one? Would spending a bundle on solar, if the payback was iffy (or the net meter deals in NC sucked) convince anyone to do the same?

I'm glad that Tesla exists, and it has had a positive macro effect on the auto industry but their cost/profit margin (needed to survive and grow) actually does little to convince the average person of the feasibility of EVs. On the contrary, people I meet say 'with enough money, you can have anything' and suppose that it will forever remain out of reach for them. So I show them my Bolt that goes as far and as fast as Tesla 3SR, and costs about half as much, while still being loaded with tech and being a very familiar dash/cabin and driving experience. And it blows their mind in a way a Tesla does not.

Big picture... I think we are getting to the point that green tech and green energy are going to get cheap. Cheaper than fossil tech (at scale, like grid solar, even if rooftop looks spendy). So green will mean SAVING money, ABUNDANCE and better HEALTH. And a lot of it will be propelled by large corporations pursuing profits, and people just looking to save money on their next purchase. We are a decade closer to that day/revolution than I was when I did all my (re)modeling. Soon enough all that stuff will speak for itself and we won't need to worry about selling it to skeptics at the margins. The adoption curve is going to be led by the big boys, the corps, and govt policies. Your vote for climate policies and climate minded pols (local state and Fed) probably has more impact accelerating that transition than jawboning your neighbors about $$$ rooftop solar.

Maybe its not clear that the change is coming sitting in NC, but it IS. After the change, we won't all be living in net-zero houses with solar panels on the roof and Tesla power-walls in the garage; that is not the goal. We will be living in the same houses (perhaps reasonably retrofit using public aided dollars) that look exactly the same, fully electrified, and with elec utility bills that are lower (inflation adjusted than now) and 100% renewable, and driving EVs that look and work like our old cars and cost less (and DCFC in <10 mins at any HW rest area).

Since the green energy and EV revolutions are already baked in, model your kids on green FOOD. More plant based, more whole grains, fruits and veggies. Less beef, less processed foods, less sugary everything. Treats in moderation rather than excess (one scoop of icecream in a little bowl with a little spoon rather than 5 scoops in a big bowl with a tablespoon). And you will be setting yourself up for good health, and them as well, adding years to all your lives, and saving the climate at the same time.
 
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stoveliker

Minister of Fire
Nov 17, 2019
6,228
Long Island NY
My first suggestion would be to get your behind in the attic with a case.of spray foam cans and silicone caulk. Lift up the insulation and seal all there is to seal, walls, penetrations etc. (Silicone at electric boxes for fire safety)

Then to putt the insulation back and add. I had r19 batts and added r38 on top (90 deg rotated).

This cost me 6 weekends (full time, tough access, no walking surface), and $2000 in batts. (And change in foam and caulk).

Be aware of ducts and chases.- the latter are notorious for making sq. ft sized.holes in your envelope.

It cut my heating needs in half for $2 per gallon oil, it's $5 now.)
Biiiiig ROI.

(And then I started heating with free wood...)

It's not easy physically (in my attic), but anyone with a decent body can do this.


Edit: my current home was built in '77. To give an idea of why the attic work mattered.
 
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EbS-P

Minister of Fire
Jan 19, 2019
3,543
SE North Carolina
I get your conundrum. You can do things to ACTUALLY save energy/CO2 to your house, but if they are invisible, then there is no 'lesson' for your kids or modeling for your neighbors.

When I did my retrofits, I **told** my grade-school age kids that I was doing it to save energy and CO2, and that it was stupid not to do it, bc I could save money at the same time... win-win-win. They got it. When they learned more about the climate later, they already knew what side Dad was on, and where he put his own attention, sweat and dollars. They have always remain convinced of that about me.

I told my neighbors (with the same house by the same 1960 builder) about the huge savings from attic airsealing and they had it done. I can tell from the snow on our rooves that their job wasn't quite as good as mine, but its respectable. They are still heating with oil (unlike me who switched in 2008), but TBH, the heat pump tech was not that great until recently, and I haven't saved a lot of money (its a wash with equipment cost). So their choice is reasonable based on engineering and $$.

I told/shamed a different neighbor to switch to a heat pump (from propane) when he did a big expansion/remodel. He cries about the January electric bill, but he's happy the other 11 months.

When I got an EV in 2014, I got a LEAF on a $200/mo lease. As a family with small kids, we ended up carpooling kids in it. We let all the kids 'plug it in' which they were excited about (at 10 yo). Their parents asked, we told them it was CHEAP and did everything we needed a (second) car to do. Eventually we gave them extended test drives. Two families we knew got LEAFs in 2015. We modeled that. Both families stuck with the EVs ever since, getting a Gen 2 LEAF and Tesla model 3s.

Does your driving the Model X around convince anyone to drop $100k on one? Would spending a bundle on solar, if the payback was iffy (or the net meter deals in NC sucked) convince anyone to do the same?

I'm glad that Tesla exists, and it has had a positive macro effect on the auto industry but their cost/profit margin (needed to survive and grow) actually does little to convince the average person of the feasibility of EVs. On the contrary, people I meet say 'with enough money, you can have anything' and suppose that it will forever remain out of reach for them. So I show them my Bolt that goes as far and as fast as Tesla 3SR, and costs about half as much, while still being loaded with tech and being a very familiar dash/cabin and driving experience. And it blows their mind in a way a Tesla does not.

Big picture... I think we are getting to the point that green tech and green energy are going to get cheap. Cheaper than fossil tech (at scale, like grid solar, even if rooftop looks spendy). So green will mean SAVING money, ABUNDANCE and better HEALTH. And a lot of it will be propelled by large corporations pursuing profits, and people just looking to save money on their next purchase. We are a decade closer to that day/revolution than I was when I did all my (re)modeling. Soon enough all that stuff will speak for itself and we won't need to worry about selling it to skeptics at the margins. The adoption curve is going to be led by the big boys, the corps, and govt policies. Your vote for climate policies and climate minded pols (local state and Fed) probably has more impact accelerating that transition than jawboning your neighbors about $$$ rooftop solar.

Maybe its not clear that the change is coming sitting in NC, but it IS. After the change, we won't all be living in net-zero houses with solar panels on the roof and Tesla power-walls in the garage; that is not the goal. We will be living in the same houses (perhaps reasonably retrofit using public aided dollars) that look exactly the same, fully electrified, and with elec utility bills that are lower (inflation adjusted than now) and 100% renewable, and driving EVs that look and work like our old cars and cost less (and DCFC in <10 mins at any HW rest area).

Since the green energy and EV revolutions are already baked in, model your kids on green FOOD. More plant based, more whole grains, fruits and veggies. Less beef, less processed foods, less sugary everything. Treats in moderation rather than excess (one scoop of icecream in a little bowl with a little spoon rather than 5 scoops in a big bowl with a tablespoon). And you will be setting yourself up for good health, and them as well, adding years to all your lives, and saving the climate at the same time.
Well said
 

EbS-P

Minister of Fire
Jan 19, 2019
3,543
SE North Carolina
I am estimating at least 1/2 of the us population lives somewhere where as temperate as Raleigh NC. Just take the population of CA, TX and FL. That’s 1/3.

Is it reasonable to think that the average person concerned enough with their carbon emissions who are undertaking energy home improvements could reduce CO2 output of their home in half?

Thinking about my home that seems like a really difficult task without solar.
 

stoveliker

Minister of Fire
Nov 17, 2019
6,228
Long Island NY
Air sealing the attic also helps a boatload with humidity (and thus AC cost) because of the chimney effect of your home. Insulating the attic (only after sealing) is similarly important given the heat on the roof in the South. At least it was for me in the stagnant, humid East TN valley.
 
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woodgeek

Minister of Fire
Jan 27, 2008
4,780
SE PA
The answer to this question requires quantification, such as from an energy audit.

Instead, you could compute your seasonal BTU/ft^2.HDD, which is pretty easy in heating. In cooling it is probably worse, bc of latent loads associated with humidity infiltration. If you are currently at 10, you can get to 5 (with 2x4 conventional construction), and reduce your heating and cooling bill by >50%, as many here have. Your home will also be a lot more comfortable, quieter and have better indoor air quality.

If you at a later date by a new heat pump to electrify your heating, the unit will be half as big as if you hadn't, and cost a fraction as much.

If your score is 6-7 already (which you seem to think it is) then you can't save 50%.

But most homes in the US were built intentionally leaky, and only a fraction have been airsealed.

So, what is your backup heat source, how many therms in gas or gallons if propane, and how many cords/species of wood? Last season.
 

EatenByLimestone

Super Moderator
Staff member
You could probably cut it in half, doing nothing, by accepting warmer temps inside in the summer and cooler temps inside in the winter.
 

EbS-P

Minister of Fire
Jan 19, 2019
3,543
SE North Carolina
You could probably cut it in half, doing nothing, by accepting warmer temps inside in the summer and cooler temps inside in the winter.
I don’t think at realistic for us. 79 summer 68 winter.
 
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EbS-P

Minister of Fire
Jan 19, 2019
3,543
SE North Carolina
The answer to this question requires quantification, such as from an energy audit.

Instead, you could compute your seasonal BTU/ft^2.HDD, which is pretty easy in heating. In cooling it is probably worse, bc of latent loads associated with humidity infiltration. If you are currently at 10, you can get to 5 (with 2x4 conventional construction), and reduce your heating and cooling bill by >50%, as many here have. Your home will also be a lot more comfortable, quieter and have better indoor air quality.

If you at a later date by a new heat pump to electrify your heating, the unit will be half as big as if you hadn't, and cost a fraction as much.

If your score is 6-7 already (which you seem to think it is) then you can't save 50%.

But most homes in the US were built intentionally leaky, and only a fraction have been airsealed.

So, what is your backup heat source, how many therms in gas or gallons if propane, and how many cords/species of wood? Last season.
At the high end I’m am 7.2 (2 cords of 25M btu pine). ( It’s hard to account for the shoulder season where we run the heatpump for an hour a day.) But I am just making an educated guesstimate. At the low end it has to be above 4 but that’s a pure guess.

If you wanted real number from equipment runtime you would need each stage runtime. And then figure in the heating strips minus and the defrost (if you want it within 5-10%) and then you need to average the the outdoor temp while the units was running(20-30% drop in output 45 vs 32) you see where this is going for all the all electric homes in the south. Even getting these numbers isn’t easy.

Really you need a good manual j and then a formula to calculate annual energy consumption.
 

stoveliker

Minister of Fire
Nov 17, 2019
6,228
Long Island NY
Rather than fretting about doing things perfectly, educate yourself on how to do certain (useful) things right (yourself). This gets you on a good path (having benefits for you and the environment) while staying in the realm of realistic possibilities.

The perfect is the enemy of the good,. especially in the field of making homes more environmentally efficient. The good things you can do now will have to be done anyway to make things perfect later (IF you can affordable to do that later) - but then they'll have had a good impact for years already.

You think a lot, and that's good. But you know that insulation and sealing will be part.of.a perfect plan anyway. So get that done (yourself) now. Take a step rather than keep planning a step.


This is not to be a ahole. Just.an observation of the threads I've read from you. You're doing good in wanting the best. Seriously. I wish more people had the drive. My only observation is that at some point making a step is needed. And here.you can make a step with minimum labor charged.
 

maple1

Minister of Fire
Sep 15, 2011
10,963
Nova Scotia
Energy audits are cheap in the grand scheme of things. That is my next step with our place. Then you don't have to waste head space on what to do and how to do it. It will then be ( should be?) all right there in black and white. I want to re- side our house the next year or two. So will be trying to step back and look at bigger pictures before that.
 
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woodgeek

Minister of Fire
Jan 27, 2008
4,780
SE PA
At the high end I’m am 7.2 (2 cords of 25M btu pine). ( It’s hard to account for the shoulder season where we run the heatpump for an hour a day.) But I am just making an educated guesstimate. At the low end it has to be above 4 but that’s a pure guess.

If you wanted real number from equipment runtime you would need each stage runtime. And then figure in the heating strips minus and the defrost (if you want it within 5-10%) and then you need to average the the outdoor temp while the units was running(20-30% drop in output 45 vs 32) you see where this is going for all the all electric homes in the south. Even getting these numbers isn’t easy.

Really you need a good manual j and then a formula to calculate annual energy consumption.
Thank you for the calculation. I would assume a COP of 2.0 in dead of winter and 3-4 in the shoulder season (with strips and defrosts). What eff did you estimate for the wood? 60%? 70%?

But yeah, with a HP it is VERY hard to gauge BTU output. I was working from an oil boiler and knew the gallons and output eff. I could time the duty cycle of my boiler on a daily basis vs the outdoor temp, and see a 5-10% change from a retrofit step very easily. After the boiler got ripped out, I could switch to strips for a day, and log run hours on my ecobee to get a precise BTU input for that day.