You need to tighten up the insulation envelope of your house big time. You're losing a lot of your indoor air thru the ceiling section without insulation, the poorly insulated attic, as well as thru your single pane windows and open fireplace. Leaking return air ductwork (especially in the attic) adds unconditioned air into the HVAC system.

Tighten up the leaky house and ductwork before you do any heating or a/c replacement. A new system has to be sized properly for the heat gain/loss of the structure.

And no, the furnace and/or a/c install is not a DIY job.

Good luck.

replacing my 30 year old unit with a new Trane HP last year resulted in a huge energry savings, somewhere in the 40% range. is this the case for everyone, no it is not. but it can make a big difference.

as stated above, you should seal up all air leaks on teh home and the ducts. this alone can make a huge difference. when teh duct work leaks you either condition the attic or you suck in unconditioned air and make the system work harder, depending on where the leaks are. jsut sealing the leaks in my ducts before i replaced the old system allowed it to work much better.

As for duct sealing use duct mastic, aluminum duct tape or silicone on all sectional seams and longitudinal seams (Do not use regular duct tape).

If you wait until January 1, 2009 for furnace and A/C replacement, the federal rebates which ended December 31, 2007 are going to be reinstated. Improvements in 2008 do not recieve these rebates.

If you have drafts, this is infiltration air which can consume more energy than heat loss. Outlet and switch plate gaskets can be installed to reduce/eliminate infiltration air through these devices.

Hope that helps,

Dan Martyn

Here is a link for the Tax credits, looks like $300.00

Here is a link that might be useful: Energy Star Tax Credits

...Some followup information....

Thanks for the replies so far!

The house seems to retain its temperature pretty well.
For example, the heat is set to go on at 60, and off at 65. The thermostat is set to run the 60* overnight sked. at 10PM. The furnace came on a couple of times starting around 4am.

I am not discounting leaky ducts, and inadequate insulation but using a good, instant read meat thermometer, the heated air temp at the registers is within 5% of the temp I measured at the heater itself.

I measured about 115 degrees at the heater registers. What kind of temp should I be seeing out of them?

The thermostat is located within a few feet of the return air duct; is that negatively affecting the operation?

Thanks again for the help!

If you have a single zone, locating the thermostat near the main return is recommended. It will sense the temperature of the return air and the furnace will shut down when the zone (Return air temp) is satisfied.

The temp at the registers with good insulation should read anywhere between 120F to 130F

Thanks for the replies!

I used an accurate instant read meat thermometer to check the temp at the supply plenum it was about 120 degrees. I also checked most of the registers and they were within about 5% of that.

The exhaust pipe is way too hot to touch.

The furnace was supposed to be an 80% efficient model, though as I mentioned earlier it is a 1991 model.

Does efficiency decrease as furnaces age? If so, what is happening that makes it less efficient? Its a simple process right, a fan blows air over a heated surface. How does that become less efficient over time?

According to our gas meter, about 4000 cu.ft. of gas is being burned up in the furnace per day. 4000x1027(btu/cuft/92000(furnace btu/hr)=44 hrs of running full blast..? The furnace only runs at most 6 hours per day, so does that mean it is really just 13% efficient?

thanks again for the assistance!

jrn

Are you moving sufficient air through the heat exchanger? Are you getting sufficient air flow out of your supplies? When was the blower assembly cleaned and serviced? Many times I see the blowers neglected to a point where they are no longer moving rated air. Are you useing filtrete filters or high density filter media? These restrict air flow considerably. What are the high/low limit switch values?

Hello, and thank you for the reply. Air 'seems' to be moving pretty well from the supplies. I don't have a way of measuring the flow though (it does blow dog hair around pretty well). Also, supplies closer to the heater move air better than those farther away.

The furnace has an electronic air cleaner component that no longer works. The filter is just a thin aluminum screen. There is no noticeable difference in performance with or without the air cleaner components installed.

I've no idea when the blower was last serviced. I would imagine it has been quite some time.

Thanks again for your help!