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: 325

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

Hal Skinner replied to Hal Skinner's discussion An example of what an RCC can do with no R- insulation in the walls.
"Mornin Brett. 90 to 85, yes a slight variance there.  Same ASTM test, different scientists,…"
14 hours ago
Bret Curry replied to Hal Skinner's discussion An example of what an RCC can do with no R- insulation in the walls.
"Great information Hal. It appears the thermal emissivity in your test was .85 rather than .90. Are…"
15 hours ago
Juan Roca commented on Dale Stephens's blog post LED Lighting - Garage Door opener interference
"Hi,There is a real problem with remote controls and LED lights. However, there is a solution in the…"
22 hours ago
Profile IconJuan Roca and Elizabeth Coe joined Home Energy Pros
yesterday
Casey Gesell posted videos
yesterday
Gerald Shechter posted videos
yesterday
Hal Skinner replied to Hal Skinner's discussion An example of what an RCC can do with no R- insulation in the walls.
"Bret,  here are the 2 reports I referred…"
yesterday
Craig Foley shared George Kopf's discussion on Twitter
yesterday

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service