I just had an energy audit performed on my house. They suggested that I insulate the crawl space, which makes perfect sense. They also suggested that I run a new heating duct to each end of my crawl space and said that I would be surprised how much warmer my house felt once the crawl space was insualte and heated.

While I don't doubt my floor would be much warmer if the crawl space was heated, does it make sense to anyone that my heating bills would go down if I also heated the crawl space? (Which is about 5400 cubic feet)

Heat rises? That's the only thing I can think of...

frankly, no. i cannot imagine the heat used on the crawlspace is less than the energy saved by doing so. I'm not an expert at all. Just a physics geek.

Insulating the crawl space alone will make for lower heating bills, but then heating the crawl space as well will probably make them the same or somewhat higher depending on a number of factors.

I'm not an HVAC expert, just an engineering geek.

In theory, insulating the crawl space will trap the heat you're losing in the crawlspace, so I would insulate the crawlspace and see if a noticable difference happens, then make a decision about heating the crawlspace. Running ductwork is no small undertaking, either.

And in doing so will probably decrease the efficiency of your furnace because, from what i've heard, they're are specific calculations that go into determining what size/brand/etc furnace is installed...

Interesting that they would suggest adding additional dudct work during just an audit. Sounds a little sales pitchy to me. I would think the purpose of an audit would be to show you how to optimize the house to use less energy not a way to increase energy consumption.
Unless the noticed a large amount of heat escaping through the floor in the crawl space area, but then a again insulating under the floor would reduce that heat loss. I don't see the point of adding heat to that area. Is the floor in this area extremely cold? What are the exterior walls of the crawl space comprised of?

Depending on the capability of the furnace (it must first be able to handle the extra requirement), the energy used would not necessarily be any more.

What this means, is that IF the furnace is capable of maintaining the same airflow to the rest of the house, then the addition of the ductwork to the crawl space will not necessarily cause an increase of energy used. The furnace will still be heating the house (actually heating the thermostat) to the same temperature, with the same amount of energy and air flow.

Now, if the furnace isn't big enough to handle the extra load, then yes, it will cause more usage, because the furnace will have to run an extra amount of time to compensate for the lost air flow to the crawl space, thus increasing the energy use.

Thanks for your feedback everyone.

THE4RINGZ wrote: Interesting that they would suggest adding additional dudct work during just an audit. Sounds a little sales pitchy to me. I would think the purpose of an audit would be to show you how to optimize the house to use less energy not a way to increase energy consumption.
Unless the noticed a large amount of heat escaping through the floor in the crawl space area, but then a again insulating under the floor would reduce that heat loss. I don't see the point of adding heat to that area. Is the floor in this area extremely cold? What are the exterior walls of the crawl space comprised of?

I would definitely be skeptical if they were offering to do any work, but this was just an energy audit provided by my electric utility.

The walls are cinder block, but most of them are under ground.

behindthelense wrote: Depending on the capability of the furnace (it must first be able to handle the extra requirement), the energy used would not necessarily be any more.

This might be a stupid question, but how can I determine if the furnace can handle the extra requirement? Is it based on how many cubic feet my house has?

http://www.alpinehomeair.com/Furnace-choosingsize.cfm#top