# Insulating a 3 seasons room floor



## Gary in WA (Mar 11, 2009)

Check with your local building department please. Require a perimeter footing or grade beam, 18" code required minimum clearance to wood joists, bearing to soil from roof loads, windows, walls, heating, etc....

Gary


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## cyprusrom (Sep 20, 2013)

The "Deck" was built with a sun-room in mind.The deck is attached to the house by a ledger board.Away from the house,it sits on two beams, each made of 3 2x10" that sandwich (2) 1/2 inch treated plywood between them. Each beam sits on 2 6x6 posts that have concrete footings 4' deep.It has a double rim joist and 16 O.C joists. It cantilevers about 12 inches. The entire structure will be only 12'x12'.
I did apply for a permit, and I was given a go.


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## Gary in WA (Mar 11, 2009)

Excellent! You'd be surprised at how many "remudels" I've seen by others over the years....

R-38 is code minimum; http://energycode.pnl.gov/EnergyCodeReqs/index.jsp?state=WisconsinOR footnote "g", lol. 

You would still get thermal bridging and moisture through the exposed joist bottoms (radiation coupled) with wood at R-1.25 per inch; http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/

The suggested 1-1/4" of plywood on the tops is safe. Do a "search" for topic at box, top of every page...a few good tiles guys around here. I'd need the closest large city near you for a dew-point calculation...

Warm on the toes; airspace at floor; http://www.buildingscience.com/documents/insights/bsi-064-bobby-darin-thermal-performance

Vapor barrier; not with that thick a foamboard (any foil-faced?), waiting on the locale...what thickness/type of sub-floor? Air-seal (caulk) the plywood to prevent infiltration.

Gary


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## cyprusrom (Sep 20, 2013)

Thanks Gary!
I live in Wausau, which is about 150 miles north of Madison, or about 100 miles N-NW of Green Bay.
After some research and other suggestions, I was thinking of using Roxul 
http://www.lowes.com/ProductDisplay...gId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1
A bit more expensive, but I thought I would get away without using a vapor barrier, maybe, since they claim is water resistant?
I am thinking, if I use a vapor barrier, would be stapled on top of the joists. How would I then glue the subfloor to the joists?
About the thermal bridging...Could I put a 1" of rigid board on top of the joists, then glue/screw the plywood/T&G OSB? I think they also make some plywood/OSB with a rgid foam board glued together.


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## Gary in WA (Mar 11, 2009)

It doesn't take much to confuse me these days, describe the floor make-up as planned.... lol. The decking plywood/OSB is around 0.75 perms (hence another vb not needed), the foam varies per thickness, need to know the materials for perms.

Marathon County, Zone 6; http://energycode.pnl.gov/EnergyCodeReqs/index.jsp?state=Wisconsin

Foam board thickness to prevent cavity condensation for your Zone; http://www.buildingscience.com/docu...ulating-sheathing-vapor-retarder-requirements

Foamboard strips on the joist tops is another option against thermal bridging if full inside coverage stops drying.

Gary


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