Insulation, Radiant and Vapor Barriers - Insulating Floor underneath a sunroom

I have a 10x20' sunroom addition that is built on a deck 2x10"p.t. studs 16" on center with a 1 foot air gap to the ground..I want to install a Warmfloor low voltage radiant heat system underneath laminate, I have a pellet stove as the winters here are fairly severe..my question is I am getting conflicting reports as to how I should insulate underneath the sub floor...some say use solid foam followed by standard bats and then seal the bottom with a thick mil poly stapled directly to the studs, others say use blown in insulation and then cover the entire bottom with plywood or the like, this seems to be an expensive solution but I would like to do the job right as I plan to use this all 4 seasons..I'm also concerned with keeping rodents/insects out of whatever insulation choice I use as well as doing a correct moisture barrier method..do the aformentioned methods sound viable, I'm prepared to eat the cost of doing it once/right...I'd appreciate any suggestions...thanks alot!

Where are you and how "severe" is your climate. Saskatoon can be colder (no moisture), but may not be as severe for your application as Nashville or Dallas.

With only a 12" gap between the ground and the joists, you certainly have a challenge regarding moisture and thermal differences. You have poor air circulation under your deck and a high moisture area.

The first step is to cover the ground with a vapor barrier (lapped, taped and sealed).

Contact the laminate supplier to see what recommendations are made for radiant heat sytems under the floating floor. Your laminate is a rather temporary floor (in comparison to a traditional solid floor surface) that cannot tolerate high moisture constents.

The suggestions you have gotten are not expensive considering the oprtions and current investment. It sounds like they may have been made by people wanting to get a job. You will have to determine the moisture situation and how to control it and where to place the vapor barrier for your location/climate.

Dick

Since you mentioned that you have a stove for winter, I would think the vapor barrier would go on the warm side, not on the bottom of the room and insulation. Putting it on the bottom would be asking for trouble because that is where the condensation would occur in the winter... and winter is when most moisture problems occur in a heating climate. (in the deep south, it's the opposite due to hot humid summers and air conditioned houses).

So I'd suggest that whatever you decide, you should first install rigid foam insulation between the joists and against your floor. The foam will provide the vapor barrier you need provided you get a tight fit. Then you can install unfaced fiberglass batts held up with straps, or install fibercloth over the bottom (stapled to the bottoms of the joists) and use blow in cellulose (more difficult but better insulation, IMO). Then you'd want to sheet the bottom with exterior grade plywood and protect its surface with some felt or housewrap.

Doesn't sound like any fun with only 12" to work in. Good job for some skinny 16 yr olds. ;)