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proper way to insulate 4 season porch floor


stacey13's Avatar
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Join Date: Feb 2008
Posts: 2
MN

02-28-08, 03:06 PM   #1  
proper way to insulate 4 season porch floor

Am wondering what is the proper way to insulate a 4 season porch floor - the 4 season porch sits about 5 feet off the ground - just had a house built with a 4 season porch and the floor is cold as HE** and I live in Minnesota so the winter is tough on me in this room - the builder claims he can't figure out the problem so can ANYONE help me with how this should be done ??

 
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XSleeper's Avatar
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Join Date: Dec 2004
Posts: 19,296
NE

02-28-08, 08:29 PM   #2  
The problem is probably undersized joists and a lack of air sealing. What we've done when we've built a 3 season room is always used 2x12's for the floor, put cleats between joists near the bottom, dropped in plywood, glued the edges of both the plywood and the cleats (to air seal) then install the thickest fiberglass insulation possible.

Rigid foam can also be used to increase the R-value, (either dropping it in between joists first... or adding it to the bottom of the joists before the sheathing) but air sealing is probably the most important thing you can do. If he just sheeted the bottom of the joists with plywood, then this is likely the source of your cold floor. Fiberglass doesn't insulate very well when -40F wind is circulating within it. Building a 4 season room in Minnesota is probably very difficult since your winters are so cold.

 
stacey13's Avatar
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Join Date: Feb 2008
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MN

02-28-08, 09:46 PM   #3  
insulating 4 season floor

the builder first built it as a deck then put down the subfloor on top of deck floor then the pad and then the carpet - below between the joists he has stuffed in two layers of really thin isulation and this floor is ice cold - he is trying to play stupid about this so I am trying to figure out how this should be done properly then present that info to the jerk - I might be wrong but was thinking it should have had plastic down between the subfloor and insulation {and this needs to be a higher R factor with a kraft face also[? ], NOT the cheap stuff he has stuffed in there} on top of the joists- also was thinking to put plastic across the bottom of the joists after all the insulation has been placed in between the joists - does that sound right or how would you do it ? - I'm not knowledgeable on the construction side of things but seems like a common sense type of thing - then again maybe I am way off here - would appreciate your thoughts on what to do - thanks

 
XSleeper's Avatar
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02-29-08, 05:45 PM   #4  
The amount of insulation that can be installed in the joists depends largely on the size of the joist. Depending on what sort of insulation he used, two r-11 batts could equal r-22 in a 2x8 floor which normally would be sufficient provided there is a dead air space. Foam board would help. A poly vapor barrier's purpose is to stop vapor from condensing as warm air leaves the home. It also is an effective air barrier that would cut down on drafts. But a vapor barrier alone is not going to make your floor any warmer, so it's kind of a moot point. I would think the insulation he used would have had a kraft facing which accomplishes the same purpose, albeit a little less effective.

At this point I think the best thing you could do is add rigid foam board to the bottom of the room, then cover it with something to conceal/protect it.

 
Joe C's Avatar
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Join Date: May 2006
Posts: 169
NJ

03-04-08, 08:50 AM   #5  
You need spray foam(iceyene etc) for a porch floor. I've got a 12 x 25 porch that is 7.5 above the ground and I can walk on the wood plank floor in the winter with just socks on and not have cold feet. Also this porch is on the windy side of the house.

 
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