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[willieG]

the best way is if you heated with someting else and could come up with a cost of what it was to heat your home last year...what type of fuel and convert that to btu..then you could determine your wood consumption by that..but i will try this  new calculator i found on the web and see what it says and maybe scott can find his calcualtion sheet and try it also.

[willieG]

scott to match your numbers i had to use +10 for the average low outside temp and 70 for the house
when i plugged in 0 outside and 70 inside i got 51,000

[Scott7m]

Well I went wild and threw in what figures I didn't know for sure and here is what I came up with,
Not accurate but let's see....

Ceiling loss is 7650 btu/hr
Wall loss is 29750/hr
Window loss 17000/hr
Floor loss 31875
Infiltration is 33048

Ceiling loss is likely off as I probably used to high of an r value

But I used a 7500 degree day with a low of -15

According to these numbers which are estimates

You would require 119,323 btu/hr to heat your home on a -15 degree day

[Scott7m]

scott to match your numbers i had to use +10 for the average low outside temp and 70 for the house
when i plugged in 0 outside and 70 inside i got 51,000

For these u use the lowest expected low, like your lowest temp u expect to see each winter

[woodman]

This won't be perfect but should be close for figures.

0 for design

ceiling 1800

half of it should be r60 the other half is maybe r20. Old style story and half with only 4" ceiling joists.

walls first 1850

new half is spray foam other half is fiberglass batts r13

second 1000

again half spray foam and half fiberglass

Floor ?

basement walls

windows and doors figure 550 sq ft

Figure something less than tight for air changes
 
2 adults, 3 kids for people

I live in Michigan

[willieG]

the chart i have found works out for woodmans house  to main floor 45,000 upstairs 30,000 and basement 10,000 for a total of 85,000  but this chart does not allow for heat leaking from floor to floor (dont know if that makes a difference or not) plus i used +10 for a low temp as that is what it took to match scotts numbers...if i used 0 for a low i get 101,000 and that is using 70 as the house temp

no tsure if this chart can be used half way accurate or not?

[Scott7m]

Ok will do

[woodman]

Well I went wild and threw in what figures I didn't know for sure and here is what I came up with,
Not accurate but let's see....

Ceiling loss is 7650 btu/hr
Wall loss is 29750/hr
Window loss 17000/hr
Floor loss 31875
Infiltration is 33048

Ceiling loss is likely off as I probably used to high of an r value

But I used a 7500 degree day with a low of -15

According to these numbers which are estimates

You would require 119,323 btu/hr to heat your home on a -15 degree day

OK thanks Scott! The other night we had -12 but spent most of the night around -5. I loaded my boiler what I would call full at 5pm, at 8am the next day all I had were coals, water temp was down around 130 so I say that was the max my boiler could do for 15 hours. I also was heating my garage but only around 55 so I don't know what that added, and a couple of showers. So is it safe to say I was using 90k-100k/btu per hour? We keep the house at 71 during the night. 

[Scott7m]

I just re did it all and used the figures you gave me.... Day and night difference

I used averages to blend foam and regular

Ceiling loss 3600
Wall loss 9606
Windows 15400
Floor loss 5250
Infiltration 13608

Total heat loss using the 0 design temp with 7000 degree days

It says you'd need around 48,000 btu/hr to maintain on a 0 degree day


Sound right?

[Scott7m]

Yea I donno, when I added in spray foam r values things went crazy on the chart

Plus I used 0 instead of -15 like before and changed the degree days down to 7000 from 7500

With that changing, I think it's likely you were in that 80-100 range on a -15 day, I'll figure it again using 7500 and -15 lol

[Scott7m]

That changed it to near 70k, but I think I over estimated some insulation values, but maybe not... 


On my own home I've used these figures, it was scary how accurate it was, I got down to then point of weighing wood at one point lol

My home was pretty cut and dry tho

[woodman]

Yea I donno, when I added in spray foam r values things went crazy on the chart

Plus I used 0 instead of -15 like before and changed the degree days down to 7000 from 7500

With that changing, I think it's likely you were in that 80-100 range on a -15 day, I'll figure it again using 7500 and -15 lol

Ya you are running into the same trouble I do when I have tried to figure a heat loss. It is a nightmare to try to figure this house out with all the diferences in construction materials. It doesn't really matter as I have always been able to stay warm even in temps colder than we just had last week. I just thought that would put some real world numbers for the capibility of my stove. I think they rate it at 4k sq ft. so for me its pretty close.

[woodman]

I am really running off topic here but, is this why I don't seem to have the creosalt issues I hear others talk about? Since my stove is kinda maxed out does that help in effciency at all? 

[victor6deep]

It keeps you efficient at going to the wood pile.hahaha

[woodman]

It keeps you efficient at going to the wood pile.hahaha

Ya tell me about it. I would like to find a way to go there a little less. My stove deff has a healthy appatite. Scotts numbers tell me what I have been thinking, my house uses a lot of btu's.