Fishhouse Insulation Question

[Squid]

I believe there were some posts about this in the past but a search didn't turn up the results I'd hoped for. With the weather finally turning colder my thoughts have turned to the fishhouse sitting in the back. I have a 6" x 12' house on wheels that has been around for 4+ seasons now. Last year a peice of the vinyl siding came off and to my surprise I found out what insulation the house had - peices of 1 1/2" styrofoam. It was no wonder that when the wind blew on the side of the house with the thermostat the heater ran almost continiously.

So here's my question. Would it be worth my while to remove the old styrofaom and insulate it with something that has more insulating value? My plan is to get some kraft faced fiberglass insulation (like a 3 1/2" R-13) and then putting a heat wrap over that before putting the siding back on. Would this help reduce my furnace run time or would it create some unforeseen problem?

[Whoaru99]

Given that 3.5" fiberglass has nearly twice the R value of 1.5" styrofoam, it should make a nice improvement in and of itself. Bear in mind though, fiberglass R value is uncompressed at the thickness listed. If you squeeze the air out to fit a smaller space, the R value is lessened.

The only concern I can think of is making it too tight and having moisture problems.

[JohnMickish]

Moisture problems are easily kept under control with wrapping the outside with Tyvek and the inside with a good poly vapor barrier. Also, the reason that people use styrofoam is because of it's resistance to mold growth. The fiberglass will support mold and it gets very heavy when wet, and dosn't like to dry out to well. Instead of using paneling on the inside have you considered using FRP? Thats the stuff they use in commercial kitchens, it's totally impervious to water, wipes down easy and dosen't support mold growth.

[danfall]

The most important thing to recognize is the greatest amount of heat loss arises in the ceilings, followed by direct drafts, then floors, then the walls.

The obvious drafts are through ice holes. Not to sound completely patronizing, but the ice holes are as bad as open windows, door drafts, followed by window drafts are probably the next biggest places heat is lost. Seals around the walls where walls meet floor would be next.

Finally, after the above list, would be the walls.

The entire system results in an effective solution.

The ceiling should be 2-3 times more insulating than the walls. The floors are also more important than the walls, but, be careful about getting insulation wet, it is worse than nothing at all generally. On the walls, if you have 1.5" expanded polystyrene on the walls, barring a lot of air leaks, you'd have an R value of 6, this would require an R value of 18 in the ceiling (fiberglass 6" or pink board (expanded polystyrene) of 4".

The R value of 3.5" of fiberglass is about 11, so you'd be just doubling the R value of the walls switching to fiberglass. You'd be far better served by making sure the ceilings are well insulated and drafts minimized, then work on the walls, but don't waste much money on the fiberglass, just add more polystyrene, it isn't good for noise, but has a better r value for an equivalent thickness than fiberglass according to everything I've read... Another thing about fiberglass, it will absorb a lot more water than expanded.

[Squid]

First of all, thanks to all the responses guys. It seems there is no one answer that will fit this question. From the various responses it seems that fiberglass is out because of the potential for mold growth and it's ability to absorb water (not good).

Also it seems that the pink board (expanded polystyrene) is probably a better bet than having just the plain styrofoam for providing insulation value. My roof is solid continious metal and seems to be insulated well. So I don't believe that is a major source of heat loss. My floor is carpeted and even on the coldest days it stays fairly warm. As for the holes I agree that something is needed to keep the warm air in. I think I have the solution for that.

This leaves one final question. Would it still be a good idea to use the expanded polystyrene (or just leave the styrofoam in place) and then wrap a heat wrap over that? My interior walls appear to have a plastic coating for some sort of moisture barrier on the inside since sweating has never been a problem.

[Big Dave2]

If you are saying that your house has the white styro in it then I would say that you would be well served to re-insulate with a denser styro like the pink stuff. Then I would probably wrap it with tyvek.The white styro also will absorb water and become useless.

The other reason not to use fiberglass insulation is because it is not rigid and could eventually fall down the wall leaving an uninsulated section at the top.

[crappace]

what about insulating the for flooors in these drop down shacks? is there a danger of trapping water up in there and it causing damage??