[Greenbuilding] energy and power terms

[nick pine]

Bob the Futureship <futureship0000 at hotmail.com> writes:

>>... 1 ft^2 completely surrounded with R2 insulation with no heat loss from
connecting pipes would have a 0.5 Btu/h-F conductance. At 190 F, it would
lose 24h(190-70)0.5 = 1440 Btu/day (0.42 kWh/day) to 70 F room air.

>Can you tell me the how you get from 1 ft^2 to 0.5 Btu/h-F conductance?

1 ft^2/R2 = 0.5 Btu/h-F.

>And just to be clear ? what was your conversion factor for Btu?s to Kwh?

1 Btu = 1/3412 kWh.

>>The 99% winter design temp in NYC is 12 F, ie it's warmer 99% of the time.

>99% winter design temp ? Is this a worst case scenario and where did you 
>get this number?

It's a statistic from the ASHRAE Handbook of Fundamentals. It's colder than 
12 F for less than 22 hours in an average year in NYC.

>>A 16' tall 70 F house with a 1" hole at the top and bottom would have 
>>about
16.6/144sqrt(16'(70-12)) = 3.5 cfm of natural air leakage with about
3.5(70-12) =  204 Btu/h (60 watts) of heat loss.

>16? tall 70 F house?  I don?t understand the 16? tall house

A 2-story house that's 70 F indoors... (Doh?)

>16.6 / 144sqrt(16?(70-12))  ?   Can you tell me what the formula is for 
>this calculation?

cfm = 16.6Asqrt(HdT) for thermosyphoning airflow between 2 A ft^2 vents with 
an H foot (H') height difference and a dT (F) temp diff.

>3.5(70-12) ?  Can you tell me what formula this is?

Btu/h = cfmdT, approximately.

Nick