Convert BTU/hr in a Manual J to actual fuel usages

I cannot find any conversion table that translates the BTU/hr heat loss in a Manual J report to the amount of fuel required to heat the building to the design temperature.  In this case I'm using propane and I have calculated the 92,000 BTU/gal using the actual BTU/Hr X Degree Days and end up requiring over 30K gallons of propane for a heating system.  This cannot be correct.  Any guidance would be greatly appreciated.

Views: 641

Reply to This

Replies to This Discussion

Morgan,
From the perspective of the energy auditor, I don’t agree with that statement.
“Actual fuel and electrical usage" is anecdotal at best”
Unless you change something, the best predictor of future energy usage is past energy usage. Now if you are going to use fuel and electrical usage, you have to have a minimum of one years data, you need to know the heating degree days and cooling degree days over that exact period, (Or binned temp data) And you need to measure the combustion efficiency of the heat source.
I will try to dig up a paper I have on the subject- the punch line was that identically built and situated houses had a 2 fold difference in energy usage based on occupant behavior. Both have identical manual J heat loss, but use very different amounts of energy. If you are trying to make rational choices based on payback, you have to know the actual usage- which is related to occupant behavior.
An example- If you are going to recommend a solar pool heater to save money- you better make sure they are actually using their existing electric resistance pool heater. Likewise recommending a high efficiency AC replacement makes no sense if the homeowner hates AC. A customer who keeps his house at 80°F all winter, uses a lot more energy than someone who keeps the thermostat at 55. Some efficiency measures that have a reasonable payback in one situation will not in the other.
The customer generally does not care about manual J- design temps, etc. They want to know what it is going to cost to heat and cool their house, and what is the best way to do it. Manual J is one tool in the box to help do this.
Cheers,
Eric

RSS

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.

Latest Activity

Jerry Lawrence posted events
16 hours ago
Morgan M Audetat replied to Bryan Pringle's discussion Dense packed cellulose in basement?
"Right you are. You have to ask: what will the cellulose contribute.  Here in Minneapolis we…"
18 hours ago
Morgan M Audetat replied to Tony Hicks's discussion Slab-on-grade Insulation
"All slabs float. We have been installing radiant floors on various slab constructions since the…"
18 hours ago
Tony Hicks replied to Tony Hicks's discussion Slab-on-grade Insulation
"2" XPS foam. I'd love an R-20. Having foam thick enough to get an R-20 would be…"
19 hours ago
Morgan M Audetat replied to Larry Schaffert's discussion How to correctly insulate exterior wall in a 1900 house?
"Sorry, I did missed the "siding nailed directly to the framing", my grandfather would…"
19 hours ago
Morgan M Audetat replied to Larry Schaffert's discussion How to correctly insulate exterior wall in a 1900 house?
"My own farm house is sided with 1/2" t&g pine boards and vinyl. We foamed then from the…"
20 hours ago
Tony Hicks replied to Tony Hicks's discussion Slab-on-grade Insulation
"Great thought! I think that would work. I'll have to put the cost together and see where I…"
20 hours ago
Danny Gough replied to Tony Hicks's discussion Slab-on-grade Insulation
"This is a tough detail because the foam on the edge of a slab doesn't provide sufficient…"
yesterday

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service