# Home heating unevenly

We live in an older (ca. 1937) single-story home heated by an LP gas furnace. The problem is that the rear of the house is always considerably cooler than the front of the house, no matter whether we leave all the doors open or not. The thermostat is in the cooler section of the house, so the heater will keep working even if it's 75 in the front and only 60 in the back. We have thought about moving the thermostat to a warmer area of the house to keep the heater from burning up our gas (currently we are looking at \$400/month!) by running so much. But that does not solve the problem of the rear of the house being so cold. My landlord said that since the heated air has to travel farther to the rear of the house, it will obviously cool some in the duct. Is there a way to prevent it. I don't know if the ducts are insulated or not, I'm sure they're not heated. The house is about 1800 square feet and near the NC/VA border between I-85 and I-95. It has four large rooms in the front around a central foyer and then the dining and kitchen in the back with a central bathroom. (jeez, this sounds like a real estate ad <g>) I hope this is enough information.
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What's the gas consumption?

Yoiks. The temp diff is 15 with all the doors open? More airsealing and insulation might help. Caulk, a blower door test, and so on. Air leaks make a house dry in wintertime...

NREL says Raleigh is 42.6 F on an average December day.

With 4 doors open and about 36 ft^2 of upper and lower vent area and a 3' height difference, 16.6x36sqrt(3)15^1.5 = 60K Btu/h might flow from front to back. If each half has 1600 ft^2 of exposed walls and ceiling, 60K Btu/h = (60-42.6)1600/Rv makes the envelope R-value 0.46, vs R1 for a single pane of glass. Is this house missing any windows or walls? :-)
Nick
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It is an air balance problem. It will take a room by room load calculation to determine the proper amount of air flow for each room. Then use a flow hood to measure the actual air flow. Use dampers to adjust the air flow til it is correct.
Could be expreme duct or envelope leakage like Nick says, but usually just poor duct design or damper adjustment.
Stretch
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That seems likely. Otherwise, we wouldn't see such a large temp difference across the house, but...

... it seems to me there must be way too much air leakage as well, given the 15 F temp diff across the house with all the inside doors open. Without the balance problem, we might just see huge fuel bills.
In a house with lots of airtightness and insulation, all the rooms would be close to the same temperature with the indoor doors open, even if the heat only came from one location. For instance, if the house above had no air leaks and 3200 ft^2 of R20 walls and ceiling, each half would only need (70-42.6)1600ft^2/R20 = 2200 Btu/h. If that flows through 36ft^2 of upper and lower doorway vents with a 6' height diff, 16.6x36sqrt(6)dT^1.5 makes dT = 1.3 vs 15 F.
Nick
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Nock, have you ever seen a home that's broken into many small rooms connected only by 29" wide openings with a single heat source like a wood/coal stove located at one end of the home? You will have quite high temperature differential. 1.3F dT? No way.
On 12 Dec 2005 08:01:04 -0500, snipped-for-privacy@ece.villanova.edu wrote:

--
\'Things don\'t bug you if you don\'t
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Sorry, I meant Nick, not Nock.
wrote:

--
\'Things don\'t bug you if you don\'t
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wrote:

Yep, it sounds like he is sleeping too close to an open crack to me.
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wrote:

difference
only
16.6x36sqrt(6)dT^1.5
too close to an open crack.. !! that would warm him.. ( well occasionally in small hot packets ).. LOL
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Stretch wrote:

Or a family of squirrels that found a nice winter home in the duct, stuffing it full of leaves to build their nest.
--Dale
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