heat loss Calculation

[NE WOOD BURNER]

So been playing with Build it solar calculator.

I got a 36 x 28 cape
r19 walls
full foundation no insulation

comes out to 41,076 btu/hr
147.9 mbtu/yr

Does this sound realistic?

seems high to me using 1.35 rvalue on foundation for avg 4' exposure above grade.

 

[DBoon]

Without knowing your specifics, it's impossible to know. But one area to check is what your floor loss is - the calculator is not really meant for a floor over a basement. If your basement is not a living space, and the floors in your house are over the basement, then the heat loss is pretty minimal compared to ceilings, windows, etc.

 

[NE WOOD BURNER]

I agree I did not consider floor loss in calc.

I treated exposed foundation walls as walls with a rvalue of 1.35

realistically 2' avg exposed so that brought calc down to 30755 btu/hr 110.7 mbtu/yr

That brought me to 5.5 cords a year. which is about right. I burn 4-7 cords depending on the year.

this calculator does put a lot of weight on the walls. so looks like I would benefit from insulating that exposed area and my sills.

 

[jeffesonm]

41,076 btu/hr at what design temp? R19 walls must be newer construction?

I went through the same exercise recently, it might be of some help: https://www.hearth.com/talk/threads/heat-loss-calculations.118325/

 

[NE WOOD BURNER]

1986 construction 2x4 walls r13

good catch!

so update
32,863 btu/hr 118.3btu/yr 6 cord

design temp @ 20

 

[Fred61]

I don't know what insulating the exposed foundation will do to the bottom line of the heat loss calc but I can give you a feeling on my real world experience. I have a walk out basement and around the corner there's a 4 foot wall with 4 feet of exposed concrete above. After eyeballing the area last summer I noticed that the sill hangs out 1-1/2 inches and keeping with my on-going hobby of insulating I decided that area would be the focus of this year's insulating project. My projects are getting smaller as I age

I covered the concrete with 1 inch blue board then screwed 1/2 inch pressure treated CDX and stucco with fiber on top. I've checked the inside of the wall several times this winter with my non contact thermometer both on the -20 degree days and on the 32 degree days and the concrete is consistently 6 degrees warmer in the insulated area.

To me that's huge!

 

[PassionForFire&Water]

We calculate based on Heating Degree Days for your location and fuel used.
In your case 9 cords of wood.
What town/city are you in.
I just like to run the numbers for fun.

 

[NE WOOD BURNER]

Cheshire county 20 miles east of Keene

9 cords is what I got in stock! had a bit more but sold to buy oil this year planning out my boiler project. learning a lot!
I burn about 6 cords in the fisher as sole heat source
I am estimating about 1100 gallons of oil this year. will know better at the end. first full year of oil for a test. never burned it here for full heating season.

 

[PassionForFire&Water]

here we go: 6 cords x 3,500 Lbs/cord x 6,050 BTU/Lb = 127,050,000 BTU over the heating season
BTU/Lb, courtesy from Jebatty.

Your biggest heat loss is in January: 35,135 BTU/hr

 

[NE WOOD BURNER]

ok then I have a 113-125,000 btu/h oil fha furnace.
what do you think I would need for a wood boiler size to accommodate this with say 1000 gallons of thermal storage?

 

[PassionForFire&Water]

Based on 1,100 gallons of oil it is 42,300 BTU/hr in January

 

[NE WOOD BURNER]

passionfor fire&water: That is a nice calculation. much appreciated.

 

[PassionForFire&Water]

Calculations based on Heating Degree Days take the guessing out of it.
You just need your current fuel (oil, propane, cord wood) consumption as accurate as possible.
For oil it's simple: call your oil guy and tell him you need it because you gone buy a wood or pellet boiler
Oil guy not gone be happy camper

TIP: NH has $6,000 rebate for pellet boiler install

 

[BillsWS]

We calculate based on Heating Degree Days for your location and fuel used.
In your case 9 cords of wood.
What town/city are you in.
I just like to run the numbers for fun.

Hello PassionForFire&Water, could you assist me in my calc? I have no clue about any of this, total newb. My house is 2000 sq ft. ICF, 13" - 14" blown cellulose in the attic, is that R38? I live in the U.P. of Michigan. Basement is 2000 sq. ft., both floors have in floor heat using an on demand tankless propane fired boiler. The basement and main floor are ICF (3" closed cell foam inside and outside with 6" of concrete in between). Windows are double pane and good quality. The house is about 5 years old. Propane co. said usage over the last year was 1100 gallons (milder winter last year). I don't currently heat my garage but plan to. It is 26 X 30, 12' ceiling. Walls 2 x 6 fiberglass insulation, ceiling being done this week, R50. Thanks in advance.

 

[PassionForFire&Water]

I took Marquette MI as reference. If you are in an other town/city let me know.
1100 gallons of Propane
4000SF in total, but this does not play a roll in the HDD calculation. It just gives you an idea on BTU/sf

The HDD did swing from 8,000 to almost 9,000 in 2011 (12.5%)

On average for the last 3 years your January heat demand is 35,300 BTU/hr, December is 32,700 BTU/hr
In the coldest year 2011, your heat demand for January was 37,900 BTU/hr

See attachment. I updated the calculation to reflect propane. I think it is correct, but check for errors anyways.

 

[MarkW]

Using the Build It Solar calculator, is the R1.8 value calculation based on standard double pane windows? It shows my proposed house build w/10000btuh losses through the glass. Yikes! I see Anderson with a R5 window and that drops my losses to 6000btuh.
Windows suck the heat right out according to the calculator.
I was running around 33000btuh for 15 degree design for my local HDD.

 

[BillsWS]

I took Marquette MI as reference. If you are in an other town/city let me know.
1100 gallons of Propane
4000SF in total, but this does not play a roll in the HDD calculation. It just gives you an idea on BTU/sf

The HDD did swing from 8,000 to almost 9,000 in 2011 (12.5%)

On average for the last 3 years your January heat demand is 35,300 BTU/hr, December is 32,700 BTU/hr
In the coldest year 2011, your heat demand for January was 37,900 BTU/hr

See attachment. I updated the calculation to reflect propane. I think it is correct, but check for errors anyways.

Thank you PFF&W. I passed this on to my sales guy.