Latest Discussions : HVAC


03:11AM | 12/10/04
Member Since: 09/11/04
14 lifetime posts
Hello. I want to insulate a porch and make it into a year round room - have just installed really good windows. Presently the porch is open underneath. I am thinking of putting 2" foam insulation (styrofoam). Do you cover that foam insulation with something to ward off critters? I have had problems with carpenter ants in the past - taken care of - but don't want to encourage a return event and don't want cats or small wild animals nesting in whatever insulation I use. Was thinking of putting some kind of sheeting over the foam, if that's the best material to use, but wonder about creating a moisture problem.

All suggestions greatly appreciated. Thank you.



12:03PM | 12/13/04
Member Since: 11/27/04
172 lifetime posts
vapor barrier goes on the warm in winter side. up against the floor. so any plastic under the insulation will encourage moisture.

you could put batts too.

but put some mesh type metal around the porch bottom to keep out the big animals. smaller mesh to stop mice. and bury the mesh 8 inches below the ground to stop animals digging under.

metal like quarter inch fabric mesh. cheap enough for the keeping out of animals or put it on the bottom of the joists if you cannot close up the skirting area of the porch.


05:53AM | 12/28/04
Member Since: 12/17/04
3 lifetime posts
I have to say that I dissagree with the vapor barrier going against the warm floor. I think what this person is trying to do is stop the ground moisture from coming out of the ground and wetting the insulation. I think I would put the insulation on the ground, then put insulation. Just my thought.


11:10AM | 12/28/04
Member Since: 09/11/04
14 lifetime posts
The porch is about 3 feet above the ground and open so I just want to block cold air and keep the room warm. I'm thinking of using the pink styrofoam hard insulation but wondering if I need to put something to cover it - or is it enough just to have the foam insulation? I don't want to creat a vapor or moisture problem by covering the styrofoam insulation.

I'm not going to use regular insulation because I don't want cats, squirrels or skunks using it for nesting.



11:50AM | 02/18/05
Member Since: 02/17/05
1 lifetime posts
Hi, I think I am living in a colder climate (no carpenter ants here) but am trying to figure out the best way to do a similar problem. I like your idea of the styrofaom under the joists but have you thought about putting and batts above the styro to increase your R value? Its a cheap way to get your floor even warmer.'For your application it may be better to use an aluminum soffit under the styro to keep out critters. Mine will be new construction on an addition but it is basically the same thing. Because of the cold climate I want to insulate the floor to about an R35 with blown in cellulose and stryrofoam around the edges. I also want to leave about a 6 inch space directly under the floor to allow a heating duct to pump some warm air into this space. My thoughts are plywood on the bottom of 2 by 12 joists full of cellulose. On top of the joists I thought about a sheet of 6 mil poly for a vapour barrier that will tie into the vapor barrier on the walls of the room above. On top of this vapor barrier (on the warm side) I am thinking of building a false floor from blocking and 2 by 4s (with the plywood floor on top) to allow free flow of the warm air under the entire floor. Does anyone out there think this makes sense or is there a simpler way to accomplish the same thing? Thanks for any input.


07:13PM | 06/13/06
Member Since: 06/12/06
1 lifetime posts
Here is my dilemma. I just built a new deck which is now perfectly level with my interior floor. I made it like this so I would literally step right out onto my new deck instead of about 8 inches down to the concrete floor. Since then, I have contemplated on a couple of ideas to include a screened in porch to an enclosed heated and cooled sunroom. I have now decided on the heated and cooled room that I will be starting the construction here in the next couple of weeks.

However, it already has an existing roof and 4x4 posts and a 2x6 deck that is about 8 inches off the ground. Since I have now decided on the enclosed room, I now need to figure out how to insulate the floor so I will not lose so much heat and cool air. Keep in mind that I live in San Antonio, Texas and it gets pretty hot here.

So, my question is this... What is the simplest and most efficient way to insulate the floor at this point without having to rip up all of the 2x6 decking and insulated underneath. I have read that most people put some type of insulated foam board, then concrete backer board, then some other type of flooring on top of that. I cannot do this, since my floor is now level with my interior floor and if I put a layer of ANYTHING on top of the wood decking, my French doors will no longer clear the floor and will drag or maybe not even open at all.

I know that this was a long post, but I felt it was necessary to explain and describe everything that is going on with this project.

If you have any information that can help me out, please let me know...

Mike Joyner

San Antonio, Texas


09:55PM | 07/02/07
Member Since: 07/02/07
1 lifetime posts
I have almost the exact same situation. My joists are 6 - 8" above concrete. Currently I'm considering putting a vapour barrier on the concrete, laying a layer of pink foam and then covering that with batts, leaving the space against the floor open. On the one hand I'm worried that then the vapour barrier is on the 'cold' side, but putting the vapour barrier above the batts will potentially allow moisture to wick up, and putting it on both sides seems like a bad idea. I'm a little stuck and would love to have some input!


06:43AM | 08/20/07
Member Since: 02/19/07
2 lifetime posts
USE the BARRIER insulation


07:13AM | 11/09/08
Member Since: 11/08/08
1 lifetime posts
I have the same exact set up only my deck is not over a concrete slab but has about 10" of clearance from the bottom of my floor joist to the dirt grade. I have put down the 6 mil plastic and have use the kaps to secure it to the perimeter face boards. I am going to be installing radiant floor heat in between the joists and also using the refelx bubble wrap insulation under the pex tubing. I need to know what other insulation I should rest on the ground andor between the floor joists? I am going to be using the 2" styrofoam board around the outside walls. Any suggestions please let me know. I would like to lay fiberglas insulation directly on the ground on top of the plastic 6mil but nervous about completely sealing this type of insulation. Once the floor goes down there will be no way to get to this insulation again without tearing out the new floor.


10:12AM | 01/11/09
Member Since: 01/10/09
1 lifetime posts
I have 12 by 16 covered deck,I would like to close in,I need to know the best way to insulate the floor.I am installing under floor electric heating.My idea was to nail 2by2 strips along the bottom of each joist,and drop in plywood to cover the bottom of each section as the deck is too low to reach under.Fill in with roxul insultion then cover with poly,but am worried about condensation


10:09AM | 06/30/13
If this helps anyone, I am planning to insulate under a covered porch that has block for perimeter walls which are about 2 1/2 feet tall, underneath is sandy bare ground. My thoughts are to lay 6mil plastic right over the grade and up the walls a foot or two to keep the moisture at bay then use faced batted (faced side up) between joists and staple chicken wire or a plastic snow fence material to the joists to help support the insulation. I bored 2 holes on either end through walls to create some type of air flow through the space and covered them with vents to keep critters out.


11:21AM | 01/08/14
hi there I have ready big deck and want to use that in winter time. I want to put pink insulation between joist because I have double deck . after filling insulation between joist how I should cover it so doesn't get any moisture in winter and rainy season.another question is can I make any convert able room on upper sack and how. please give some idea.


08:36AM | 09/20/15
I have a porch open to the elements which has t&g mahogany decking material. The porch deck sits upon a foundation wall of an unheated basement. I am renovating a 100+ year old Cape cod cottage and the water main enters the house under the deck and is about three feet below the capped flooring. The house main water pipe is 1/2" and must be brought to code of 3/4". So, I am attempting to find best way to accomplish this. Dig and repair concrete flooring or insulate cellar (which I intend to do anyway) and allow piping to run exposed. What is best way to insulate porch floor in order to retain heat in cellar but also allow enough air to circulate under deck so it will allow decking to properly react to the environment.
I am also concerned with water finding its way between t&g connections over time?


03:35AM | 09/02/16
A contractor I hired to Insulate under my 3 season porch floor has used regular pink insulation (R-27) but it has fallen out FOUR times so far & now half of it is on the ground. They used those "springs" to install the insulation but to no avail. I want to complete this myself. What is the CORRECT way to install this insulation? Is it the right TYPE of insulation OR should it use it for another project & buy another type?


02:49PM | 04/25/18
A lot of questions but no answers! I have a screened in decj that I have enclosed with windows and walls. I want to insulate the floor and then put either carpet or laminate down. The deck is about 4 feet above the ground. I'm not trying to use the room in the winter, but want it to be 3 seasons. I too was going to use Styrofoam sheets between the joists. Any advice?


12:53PM | 05/29/18
I have an enclosed porch 20' off the ground. I wanted a good three season room (unheated) so I used 1" X 14.5" X 48" foam boards against the underside of the deck boards held in by 1" X 2" X 2' strips about every 2'. It's enough to keep the wind and chill out and will allow me to install a vinyl plank floor topside.


02:30PM | 09/26/21
We can not insulate under the deck can something go over top


03:19PM | 04/07/22
My sun porch floor is 7’ above the ground The beams 9 3/4 “ apart
I was thinking of insulating the floor then cover with pressure treated plywood
I was going to use flat foam about 2” thick

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