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Hello,

My wife and I recently (september) purchased a 44 year old home in Indianapolis IN. Prior to having the home listed, the previous owner had a pre-listing home inspection in Feb 2012 where the inspector noted a six-degree temperature difference between the rest of the house and a southern wing to the house. This wing is part of the original house, is one story, has about R44 attic insulation (we had it re-insulated upon moving in) and has three rooms: an office/den, a guest master bedroom with 4-piece ensuite bath, and another full bath. This wing is over a crawl space, which has no exterior wall crawlspace vents. However, due to storage equipment blocking the access to the crawlspace, it was never actually inspected. The original owner had her heating company evaluate the temperature difference, and they recommended a zone heating system.

Based on this information, I had a couple companies come by to give quotes on the attic insulation and zone system installation shortly after we moved in. By this point, of course, the crawl space access panels were unobstructed and we discovered that the ducts leading from the main supply trunk to those rooms in that wing had actually fallen apart. So, we figured re-connecting the ducts would solve the problem.

However, it did not. In the interim, my parents visited and my father suggested insulating the ducts themselves. My heating company did so and in the process found another duct in that crawl space which had actually been disconnected. However, despite that, there is still quite a bit of difference in temperature, sometimes ten degrees when it is exceedingly cold outside.

I have had several companies come in and offer contradictory suggestions on how to fix the problem, so I am looking for additional advice.

One major theme involves encapsulating the crawl space with insulation of the band boards. Most companies who offer that service CAN also install 4" foam board insulation along the concrete walls but recommend against this, as its cost savings are minimal without several years' worth of deep freezes. Of those who recommend band board insulation, some recommend foam board, some foam board with spray foam to anchor the edges, and some batt insulation.

Other companies recommend pulling off the insulation on our subfloor, pulling off the insulation we just installed on the ductwork, and adding a supply vent to heat the crawl space, with reinforcement of the band board insulation.

We don't really have a moisture problem at all, the crawl space is bone dry even when it is pouring rain outside, so with a 12 or even 20 mil piece of plastic encapsulating the crawl space I can't imagine it offers much in the way of insulating value. Furthermore, I'm not really sure I buy the "heat the crawlspace" theory, because, in effect, with the ducts disconnected, the crawl space was being heated in Feb and there was still a temperature difference.

So, what would folks here recommend? What solutions have you all found that help?

Thanks and have a great day!

PWH,

Here is a white paper on the benefits of a conditioned crawlspace. Link is a pdf. http://www.buildingscience.com...erformance-and-codes

It sounds to me like you're not getting enough heat to this space. The thermostat is likely in another part of the house and it is being satisfied before the addition and shutting the heat off. Zoning the heat or installing a separate unit for this room may be a good solution. Does the AC cool the space sufficiently in the summer? Is the floor of your addition insulated? What is the floor temperature like? I like the concept of a conditioned crawlspace for a number of reasons, I'm not sure it would fix this particular problem but it is a good thing to do for the long term health of the structure. What did the HVAC company say when they looked at setting up zones in your house?

One thought on supplementing the heat would be to install hydronic heating. It can be retro fitted from below since you have access to the area via the crawlspace. A small water heater (gas preferred) could power the system. You could even set it up to be supplemental heat for the colder times when your force air system won't cut it.

http://energy.gov/energysaver/...cles/radiant-heating

http://home.howstuffworks.com/...t-floor-heating1.htm

This message has been edited. Last edited by: Sparky,

quote:

Originally posted by Sparky:

It sounds to me like you're not getting enough heat to this space. The thermostat is likely in another part of the house and it is being satisfied before the addition and shutting the heat off. Zoning the heat or installing a separate unit for this room by be a good solution. Does the AC cool the space sufficiently in the summer? Is the floor of your addition insulated? What is the floor temperature like? I like the concept of a conditioned crawlspace for a number of reasons, I'm not sure it would fix this particular problem but it is a good thing to do for the long term health of the structure. What did the HVAC company say when they looked at setting up zones in your house?

http://energy.gov/energysaver/...cles/radiant-heating

http://home.howstuffworks.com/...t-floor-heating1.htm

Hi sparky, thank you for your reply.

Technically this wing is not an addition, it is part of the original house. However, you are correct that the thermostat is several rooms away probably 20 feet or more.
There is some insulation (looks like batt) under the subfloor but there are areas that are absent or thin. I did not notice a tremendous difference in the air conditioning performance during the few weeks when it was unseasonably warm this fall.

Regarding zoning: of course everyone wanted to suspend detailed recommendations on the zoning until we re-connected the detached ductwork. However, one company felt like our supply trunk was too big. They said my lennox heater is probably the top of the line for my size home, but with a supply trunk that was too large, the air wouldn't pressurize sufficiently. Personally, I'm not sure I buy that explanation since there is a natural "resistor" at the level of the duct take offs to the individual rooms, and I was always taught in engineering that when the resistance is low the flow increases if pressure remains constant (Ohm's Law). In any event, this company felt that installing a zone system would be laborious because of the trunk size but more importantly because of the multitude of take offs and branches supplying the upstairs and the northern sections of the house. Another company actually recommended the exact opposite: putting in a slightly larger supply trunk, before it reaches the branches to the individual rooms.

I saw the responses over at DIY as well. A lot of options, but sight unseen we can only offer suggestions. I'm not a HVAC guy so see my disclaimer below. ;-)