[Greenbuilding] Slab heat loss calculation

[Reuben Deumling]

I very much agree with Sacie.


On Sat, Aug 24, 2013 at 6:49 AM, Sacie Lambertson <
sacie.lambertson at gmail.com> wrote:

> As an inveterate wood burner, welcome back to the list Norbert; perhaps
> you've been just lurking, but we welcome your sensible active
> participation.  Over the years we've been fortunate to have a number of
> greats on the list, many of whom have moved on for whatever reason, I truly
> miss all those distinct personalities who could offer a wealth of
> information or simply make this list fun to read.  It is fine when one of
> these good people come back.
>
> Sacie
>
>
> On Sat, Aug 24, 2013 at 6:27 AM, Norbert Senf <mheat at mha-net.org> wrote:
>
>> A 5 lb piece of wood burned at 70% efficiency gives about 32,000 BTU.
>> That would cover the slab heat loss for 7 days. For a 5 month heating
>> season, it would need 100 lbs of wood. Doubling the foam thickness to R20
>> would save about 50 lbs of wood per year. At $240 per cord, that's a saving
>> of about $4.00 per year.
>>
>> At $1.50/sq ft for the extra foam (not counting labour), 900 sq ft would
>> cost $1350, for a simple payback of 337 years..........N
>>
>>
>>
>> At 05:44 AM 8/24/2013 -0400, you wrote:
>>
>>> RT <archilogic at yahoo.ca> writes:
>>>
>>>  ... In putting our pants back on frontwards, someone noticed that we
>>>> had all received tattoos onto our backsides:
>>>>
>>>> ? ? ? ? ? "? q? =? A [ dT ( K/s + hc ) +? ( ? * T^4 ) ]? "
>>>>
>>>
>>> How do you estimate slab heat loss?
>>>
>>> After lots of finite difference network ground loss calculations
>>> Professor Kelly Kissock at U Dayton http://academic.udayton.edu/**
>>> kissock/http/EEB/Energy%**20Efficient%20Buildings_1.htm<http://academic.udayton.edu/kissock/http/EEB/Energy%20Efficient%20Buildings_1.htm>says an A ft^2 slab on US Rf foamboard with Rp vertical perimeter
>>> insulation down "to the footer" would have an approximate
>>> A(0.1140/(4+Rf+Rp)+0.8768/(16+**Rp)) Btu/h-F conductance from the room
>>> air temp to the 4 meter deep ground temp.
>>>
>>> For example, a 900 ft^2 slab on R10 foamboard with R15 perimeter
>>> insulation would have a 900(0.1140/(4+10+15)+0.8768/(**16+15)) = 29
>>> Btu/h-F conductance from a 65 F room air temp to a 58 F deep ground temp,
>>> so the room would lose (65-58)29 = 203 Btu/h to the slab.
>>>
>>> How much would this change with different perimeter insulation depths?
>>>
>>> Nick
>>>
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>>
>> ------------------------------**-------------
>> Norbert Senf---------- mheat(at)heatkit.com
>> Masonry Stove Builders
>> 25 Brouse Rd.
>> RR 5, Shawville------- www.heatkit.com
>> Québec J0X 2Y0-------- fax:-----819.647.6082
>> ---------------------- voice:---819.647.5092
>>
>>
>>
>>
>>
>>
>>
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>
>
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