Leaning towards heat pump

Teemok

We were never comparing a completely cold basement vs an insulated one. If the 1st floor is larger than the foundation ft print all 10% downward loss figures are off.

Sticking with the box: 8' walls (768sqft), flat ceiling (576) =1344 sq ft to the deep cold and the lid has a higher TD. The floor of the pre insulation project has the boiler moderating with the earth temp of the floor and part walls. It's not outside air. Lets say it's not freezing but not warm. The coldest air in the 1st floor space is in contact with the warmest of the basement air. Maybe a 25°F TD. The floor is a bit under a third of the heat transfer area and has the lowest TD. Factor in glass and doors Could be a bit more than 10% down but not much. R13 walls and R30 lid are typical.

Wood is generally R1 per inch. 1.25 inch is R1.25 the U value of the floor is 1/1.25= U0.8 so (area)567 x U value .8 x (TD) 25 = 11,340 btu/hr loss down. Insulated R19+R1.25 floor with a 45°F TD is a 1,250 btu/hr loss. Savings of 10,089 btu/hr. with a cold basement but with the warm boiler is down there, glass in the floor might save 10,376 btu/hr compared to without the glass. If a therm of nat.gas is $1.50 and you get 70% of the btu out it's about $0.22 an hour saved. 3 solid months of heating saves $475. So 2-3 years pay back. $425+tax for 12 rolls.

Let's say the basement wall insulation project saved all the 11,340/hr downward loss. That saves $0.24/hr X 3 months $518 saved. $5000/518 = 9.65 yrs

This is not modeling but for the sake of comparison. It's more complex than either of us have represented.

I'll say it again: If you are concerned with all the other benefits (B,C,D…) of insulating the basement walls it's a good Idea.

If you are just trying to capture boiler losses it is not.

JakeCK

You're right it is more complex then either of us are representing.

But I was going with 7' high walls in the basement because that is common in older homes. It wasn't until maybe 80's that 8 or taller basements became common simply because they weren't meant to be finished.

Run those numbers with a 56' x 36' ranch on basement.

Teemok

The floor area directly above any basement is just that area. The TD and what side is hot determines losses or gains. The wall heights, space volumes, leakages, boiler losses, didn't matter to my point. Either there is boiler heat losses left over after the basement heat loss takes its chunk or there is not. A 10'x10'x7' basement with a 250k ci boiler in it will have surplus to give up to the above 10x10 area. A 30x56 with 8' walls windows and a bulkhead probably won't. I think, if we were talking face to face, this conversation would have likely have been much shorter while getting to the same place. Thanks for the effort in clarification.

LRCCBJ

Wood is generally R1 per inch. 1.25 inch is R1.25 the U value of the floor is 1/1.25= U0.8 so (area)567 x U value .8 x (TD) 25 = 11,340 btu/hr loss down.

I do not see a TD of 25 in just about any scenario:

1. The floor of the first floor will not be more than 65F
2. The ceiling of the basement will most likely have an average temperature of 55F (possibly more!). This presumes the boiler is raising the temp of the basement by 5 degrees (and the ceiling of the basement by a greater amount) when it is operating. More like 4500 BTU/hr loss down.

Teemok

I was thinking 0°F OAT and no basement wall insulation 2' exposed. All this discussion revolves around a boiler loss to basement loss ratio that creates a loss or gain for the 1st floor. I think a typical for the structure sized boiler loss and earth heat offerings wouldn't overcome the basement losses to the very cold walls and the temperature would drop. Again, the size of the boiler loss is a critical factor and the size of the basement losses is a critical factor. If 25btu/sqft is typical 14,400 for 567sqft is close to the total loss. You're right. 11,340 down is off. Air movements or not above and below the floor would make a big difference in transfer rates, 25 TD was based on 40°F down there after 24 hrs of 0°F OAT. That's not right especially in the joist space with heat transferring down. Admittedly it's a wild guess. I said I wasn't attempting to model anything. Last structure with like situation I have personal experience with was 36 years ago. There's no way to prove anything until there's a fixed case, something we don't have .Individual ideas about what is being talked about makes the effort a bit pointless.

Teemok

It would be simple enough to measure T's 1/8" off the floor on both sides along with the average T's of both spaces. Still air might make the above and below the floor difference quite low. Heat going down might have a different dynamic than heat going up.

LRCCBJ

I agree with the analysis of 25DT IF the building suffers 24 hours of 0F OAT, But, this is the extreme scenario that might occur once per season in typical NE winters. If we are talking about MN or AK it's a completely different result and your 25 DT is certainly valid.

A decision on insulation should probably be made on the average heatloss over a six month period, For that scenario, my value of a 15 DT is far more reasonable, again, with the assumption that the "average" OAT is approx. 25F for six months.

The significant number of large variables that affect this result certainly makes the effort a bit pointless. You'd need a specific building at a specific location with specific construction to make any reasonable analysis.

Teemok

So I've got these three things interacting. Should be easy enough to model right? https://preview.redd.it/bhfi2oxk13md1.gif?width=1000&format=mp4&s=074d5ac1ffe0a29bf5967a197047f30ac4522c6c

Jamie Hall

Dear me. Does anyone have a wooden stake? Or maybe a special silver bullet?

A thought on realistic outdoor temperatures. They are usually seem to be available, but often don't take into local variation. If one is actually designing something, it's best to do a little research on that. For example, while I agree that cost/benefit of insulation is best evaluated using long averages, the comment that "24 hours of 0F OAT … is the extreme scenario that might occur once per season" is not true at my specific location in northwestern Connecticut. Last winter, for instance, we had three straight weeks when the daily HIGH temperature stayed below 0. And no one regarded that as extreme…

And a thought on the modelling. One can have a lot of fun setting up a spreadsheet to do that sort of thing. You don't need specialised software, but it does help if you are good at cell equations and such like. And it really is fun to fiddle with.

:

JUGHNE

Hang on Jamie, we should be getting out of the doldrums within a short month.☺️

Teemok

@Jamie Hall I think……pokes at it with a stick, It's dead.

I use a spread sheet for a bread making process. I plug in what the desired loaf size and count is and resulting total dough weight and ingredient weights spit out. I can see hydration rate % changes if I alter ingredient ratios. How much starter/chef I need to began tripling the day before. It's a great time saver and more consistently accurate than my, on the fly back of envelope stuff.

LRCCBJ

Last winter, for instance, we had three straight weeks when the daily 

HIGH 

temperature stayed below 0. And no one regarded that as extreme…

Here is the temperature history of Bear Mountain CT for the coldest months of the winter:

You'll notice there were only three days where the temp remained below -18C………….

I would regard that as extreme, especially if you review the curve.

https://www.visualcrossing.com/weather-history/Bear%20Mountain%2C%20CT/metric/2023-12-20/2024-02-29

pecmsg

Where is it here:

ASHRAE climatic design conditions 2009/2013/2017/2021 (ashrae-meteo.info)

Jamie Hall

Which is exactly what I mean by using truly local data…