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
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.
thx in advance
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? :-)
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.
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.
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, email@example.com wrote:
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