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: 289

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

Tom Mallard replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Right, that reinforces my understanding of how it works, I was after what to plug in for values in…"
3 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Products like these dont have an R-rating. You still have to have the R-rated insulation to meet…"
4 hours ago
Graham Irwin replied to Tom Conlon's discussion Whole House Fans - Love 'Em or Not?
"Thanks for the input. The next question to ask is "how much cooling power is delivered in each…"
5 hours ago
Brandon Walton commented on Brandon Walton's blog post 12 Things Every Home Performance Contractor Should Have on Their Work Truck
"Totally off topic William, but yeah could use a bit more I suppose "
5 hours ago
William H Nickerson commented on Brandon Walton's blog post 12 Things Every Home Performance Contractor Should Have on Their Work Truck
"One more thing...you need a little more bend in that cap"
6 hours ago
Tom Mallard replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Sounds like the perfect, thin insulator adding enough thermal inertia to separate two masses and/or…"
6 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"OK Tom, I think I am on the last questionow,,,I think.  LOL Going under the building and…"
8 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Tom, sorry for having to break this up but my responses I guess are too long. You talking about the…"
8 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
" "
10 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"I guess I got too mlong winded ther, it cut me off. 1.  Spray the coating on the ducts, plenum…"
10 hours ago
Kurt Shafer replied to Tom Conlon's discussion Whole House Fans - Love 'Em or Not?
"Jan, Here are some facts. the 30 inch fan from Home Depot (not one I would recommend) is rated at…"
10 hours ago
Hal Skinner replied to Hal Skinner's discussion Rooftop A/C units and exposed ductwork in the group Radiant Control Coatings
"Hi Tom. It looks like I will have to start off most of my answers to questions with this…"
10 hours ago

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service