Hi,  We live near Anchorage AK, our home is new to us but 6 years old.  We had an energy audit done and would like to make some improvements for energy savings and comfort.  We are thinking of gutting the basement and adding radiant heat on top of the concrete slab, replacing the oversized forced air furnace and adding rigid foam insulation along with spray foaming the rim joists.  We would hire pro's for the furnace/heat.

The basement is much colder than the rest of the house and the heated air just seems to go up the stairwell we have to use space heaters to be able to use the basement in the winter.  It is a daylight basement mostly finished, concrete floors with pad and carpet, air returns are in the ceiling.  There is a fireplace (ng heatolator) that makes the basement smell like gas fumes so we dont use it much it gives me a headache. Our furnace is a york diamond 90 that runs on a high speed and cycles on and off frequently and is loud.

of course we thought the house was efficient when we were told it was 5star rated.  Our heating bill is 4 times what the energy rater stated it should be when the house was built.

What is the most appropriate and cost effective way to deal with this cold basement?  We have a guestroom, bath and tv area in the basement and a unfinished area that is supposed to be my art studio.

I would appreciate your input.
Sincerely
Kelli

Insulating the walls with rigid foam and air-sealing the foundation sill & band joist is an excellent start. If you're not putting at least 3" of polyiso (~R18) on the wall, adding a studwall on the interior side of the foam with unfaced R13 rock wool batts can fatten out the R pretty cheaply, but you'll have to do the rough dewpoint calc for your location to determine the minimum amount of foam on the above grade section, but 2" of XPS or 1.5" of polyiso would give you some margin, provided you're not too far inland from Anchorage.

Is the slab insulated? (I don't know if that was required by code in Anchorage in 2006.) In a walk-out basement adding 2" of foam above the concrete and adding a radiant heated subfloor could have some construction issues regarding the door framing, etc. If you don't know, you could find out by drilling through the slab all the way down to the gravel and figure out what's there. Drill at least a 3/8" hole so you can probe and see what's going on. You can seal it up with 1-part expanding foam when you're done. If you don't have at least 2" of foam under the slab you'll have to add at least that much on top to keep the heat loss out the bottom of a radiant floor reasonably bounded.

The gas fireplace may suck more air into the basement, and if you're not using it it's just a 24/365 infiltration leak. The fact that you can smell it means it probably is a type that use room air for combustion, and may not have an adequate combustion air supply.

The Diamond 90 shouldn't be too loud if the ductwork is correctly sized and well sealed. The on/off frequency is a function of the hysteresis of the room thermostat, which is programmable in some models. Oversizing hot air furnaces has remarkably little effect on the operating efficiency (unlike with cast-iron boilers), and even if it's running bursty 2 minute on cycles replacing it won't change your fuel use. Sealing the ducts with duct mastic (assuming rigid ducts) and sealing the seams of the air-handler of the furnace with FSK tape may help it out some.

Unless you're committed to radiant floor, defer the decision on swapping out the furnace, but if you intend to continue to use the ducts for distribution sealing them is a must. If you ARE committed to the radiant floor and continuing to use ducted air for the rest (zoning the basement separately) you can get there by replacing your WATER HEATER with a condensing Vertex or Polaris more cheaply than a condensing boiler/hydro-air solution, and use a cheap 2-stage condensing gas furnace that's appropriately sizes for the "after" picture of any building envelope upgrades.

Any time a house is using 4x expectations I suspect huge air leaks and possibly hidden missing insulation. An energy audit that includes a blower door test and infra-red imaging to track down the defects is in order.

Having the basement return air located in the ceiling in your climate is simply poor design. The warm air supply registers are also likely in the ceiling. Elementary physics will tell you that the warm air is less dense and will layer near the ceiling and simply move to the return register or up the stairs. One of the first things you could do if the tear-down-rebuild it yet some time in the future is to move your basement return air from the ceiling to a baseboard/low wall location. Think of the return register like a big vacuum cleaner sucking up the cold air layered near the floor. In addition make sure that there is enough undercut space for the doors on any rooms allowing the return air to circulate to the low wall return air opening. A door on the stairway might also help.
Does your NG Heatolator have any sort of outside combustion air ducted to it or do you have anysort of makeup air venting into the house? It is quite possible that if your house is relatively tight that when running bathroom or kitchen vent fans you are drawing combustion gases back into the home while it is firing. If you can feel cold air inside the firebox with no fire and you are running exhaust fans elsewhere in the house that is very likely the case.

Posted By KI7OM on 10 Jul 2012 08:51 PM
Having the basement return air located in the ceiling in your climate is simply poor design. The warm air supply registers are also likely in the ceiling. Elementary physics will tell you that the warm air is less dense and will layer near the ceiling and simply move to the return register or up the stairs. One of the first things you could do if the tear-down-rebuild it yet some time in the future is to move your basement return air from the ceiling to a baseboard/low wall location. Think of the return register like a big vacuum cleaner sucking up the cold air layered near the floor. In addition make sure that there is enough undercut space for the doors on any rooms allowing the return air to circulate to the low wall return air opening. A door on the stairway might also help.
Does your NG Heatolator have any sort of outside combustion air ducted to it or do you have anysort of makeup air venting into the house? It is quite possible that if your house is relatively tight that when running bathroom or kitchen vent fans you are drawing combustion gases back into the home while it is firing. If you can feel cold air inside the firebox with no fire and you are running exhaust fans elsewhere in the house that is very likely the case.

Seriously, do the math on the elementary physics rather than mere arm-waving arm-chair physics! 

You'll find that the stratification forces over a 9' tall room are really quite modest- orders of magnitude behind the air mixing motion induced by air handlers.  In the bursty on/off mode this system is running the mixing of the air would be pretty good. Only over relatively long periods of undisturbed air would the buoyancy factors induce stratified temperatures in the room.

If there's a temperature gradient in the room it's likely to be from a significant heat-loss out the slab &/or outdoor air infiltration at a low point, or a very-cold door/wall is inducing a convection current. (More likely a combination of the three.)

Moving the return register to floor level won't fix the cold-feet/warm-head problem one bit.  Moving the SUPPLY register to floor level. and directing it across the floor would help some though.  But in a tight well insulated house you shouldn't have to move either to be comfortable. (Tightness and insulation levels are suspect here though.)

Good call on testing for backdrafting on the fireplace, which seems likely given the reported gas-odor issues.  There could be other issues related to that unit that could account for the symptom, but backdrafting is a serious health hazard, something that needs to be rectified.

A good IR thermoscan would be helpful to determine if the walls are properly insulated and if there is excessive air infiltration around the sill and rim joist. The more information you have before you start tearing down walls could save you a lot of grief, time and money.

My comment about moving the RA register to the floor was ONLY if the other insulation and sealing options were not to be undertaken in the near term. Depending of the exiting construction, placement and access to the RA plenum it could be relatively easy and inexpensive or simply not practical. How much it may help would be dependent on the temperature, volume and velocity (250- 450 f/s recommended) of the supply air and the size and number of runs. Back in the 70’s and 80’s if the homeowner or general contractor wanted the basement to really be comfortable we would install a separate counter-flow furnace in the basement over a concrete plenum with PVC ducts buried below the slab grade. Of course then there was little concern about the amount of heat loss and in our high desert area there is also little concern over ground water.

I seem to recall the York Diamond 90’s as having multistage burners and modulating blower motors – perhaps not. The short cycling though is problematic. That usually is an indication of oversizing but in this case it could also be any number of other issues such as improperly set manifold gas pressure. KelliSean could also see if there is an option to run the furnace blower consciously on a lower speed. Older single heat exchanger furnaces could be derated relatively easily but not so with the newer HE and condensing furnaces but that is where a properly sized furnace with multistage burners come in handy.