# Insulating under an already-built mudroom?



## edge-of-the-woods (Nov 23, 2016)

Can you blow in or spray in insulation under an already-built structure?

There is a mudroom on our house that used to be the front porch - the past owners converted it.  It's really nice, but gets cold as can be.  There is no door between the mudroom and the rest of the house, and that whole end of the house is about 5-8 degrees colder because of it.

Recently we removed some pipes in the ceiling of our basement, and I was able to get a good luck under where the mudroom is built.  The whole thing is off the ground, and the whole cavity underneath is empty.  Not a stitch of insulation in a space that's about 10' wide by 12' long and 6" high.

I'm wondering if I can just push in a ton of fiberglass batting to add some insulation.  I'm just worried about mold and mildew under there afterwards. 

Anyone have any ideas?  Thanks!

Also, we can't close the mudroom off from the rest of the house with a door, because it's also how the dogs go in and out at night or when we're not home.  And then the mudroom would be freezing.  We can't relocate the dog door.


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## Strange82 (Nov 23, 2016)

So, is there free flowing air in the cavity below? Way type of rodent activity do you have in and around your home?
I ask about air flow because that will make a difference with condensation. I  always try to ensure good air circulation  in crawl spaces. 
The best option (most expensive) is have spray foam sprayed onto the bottom of the floor boards. You will get no air leaks and the rodents won't build nests in it. You can get a square foot price. You can also buy do it yourself kits that cost about $600 I think. 
Next is the old fiberglass bats. Use faced stapled to the bottom of the joists and there you go. You can buy peppermint oil and put it in a spray bottle and it will discourage rodent activity. 


Sent from my iPhone using Tapatalk


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## iron (Nov 23, 2016)

yes, spray foam or xps foam with cans of spray foam to seal the edges.


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## velvetfoot (Nov 23, 2016)

This space over ground  is 6" high, right?


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## edge-of-the-woods (Nov 23, 2016)

So the space is only accessible through an opening that is 2" high by 3' wide.  It was previously obscured by an iron pipe.  

Now that the pipe is gone, I can see the opening, and I don't think it is much more than 6" high.  At best it might be 8" or 10" high.

That's why I was thinking spray foam, or pushing loose fiberglass through the opening with a long pipe, packing it full.

There's no way I can get inside.


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## velvetfoot (Nov 23, 2016)

This is a job for someone actually knows something about this.
I can see moisture being an issue with fiberglass, but I've heard termite boring through foam to get from the ground to the wood.  Maybe they have termite resistant spray foam.  I'm not sure you can just pump it in there-it expands, right?  Maybe they make non expanding foams?


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## festerw (Nov 23, 2016)

For a temporary fix you could hang a thermal curtain in the doorway.  Dogs can still get through but you won't have near as much cool air into the house.


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## xman23 (Nov 23, 2016)

It's a porch, and a bad conversion to heated living space. How good you fix it all depends how much you want to spend.


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## rwhite (Nov 24, 2016)

Or just add a door.


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## Lake Girl (Nov 25, 2016)

edge-of-the-woods said:


> pushing loose fiberglass through the opening


We had a similar front porch.  Loose fiberglass really won't help the situation as it allows air to infilitrate in the cavity.  Spray foam insulation appears to be the best way to stop that and insulate.  Just have to figure out how to spray the perimeter/underside of the floor boards...


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## mcdougy (Nov 27, 2016)

Pull up the plywood floor is about your best option., this will give you needed access. I would suggest laying voupour barrier on dirt then spray foam to that or foam board. Cut the plywood 4 " away from wall and put short blocks in to hold plywood when insulating is finished. Wifes love to go shopping for new floors!


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## Lake Girl (Nov 27, 2016)

mcdougy said:


> Pull up the plywood floor is about your best option., this will give you needed access. I would suggest laying voupour barrier on dirt then spray foam to that or foam board. Cut the plywood 4 " away from wall and put short blocks in to hold plywood when insulating is finished. Wifes love to go shopping for new floors!


Not a bad solution either ... just make sure saw blade is set at the right depth so floor joists don't suffer large cuts.  Instead of blocks, I would put full 2x? supports between joists for better stability.

What is the current floor covering in the mud room?


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## Mt Bob (Nov 28, 2016)

Pull up floor,if you have lots of time.If was mine--drill lots of holes(prob. 2",sprayer contractor would know),along the beams,and near sills,have contractor spray and fill complete(as he/she can),then add another layer of flooring.Closed cell foam will eventually draw moisture,breaking it down,but not in your lifetime.Make a few phone calls to spray contractors,run this by them and see what they say.It will be expensive,as will need high expansion rate foam,and lots of it.If holes big enough,can even funnel down some gravel ahead of time.


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## mcdougy (Nov 28, 2016)

bob bare said:


> Pull up floor,if you have lots of time.If was mine--drill lots of holes(prob. 2",sprayer contractor would know),along the beams,and near sills,have contractor spray and fill complete(as he/she can),then add another layer of flooring.Closed cell foam will eventually draw moisture,breaking it down,but not in your lifetime.Make a few phone calls to spray contractors,run this by them and see what they say.It will be expensive,as will need high expansion rate foam,and lots of it.If holes big enough,can even funnel down some gravel ahead of time.




Thats a mediocre remedy, it's a 10' x12' room = 4 sheets of plywood. It's 2 hours max well spent. Allows you to see everything.....wires, mould, joist condition, and get a layer of vapor barrier down to cover the dirt. Laziness never pays, we all know that.


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## sportbikerider78 (Nov 28, 2016)

I'd pull it up and use it as an opportunity to put a nice tile floor down.  1 day project start to finish is for you and your best drinking buddie with a remodeling problem.

I'd insulate with xps, then new decking, then cement board and heated tile.  But I'm a bit nuts with projects.


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## Oregon aloha (Nov 29, 2016)

I've delt with this before. keep the air space if you can. the thing to do is raise the floor in that room by 2" by laying 2x4's on there side and putting solid 1 1/2" foam insulation in-between and then your ply and flooring .


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## edge-of-the-woods (Nov 29, 2016)

Thanks everyone!  The floor is already tiled, nice big stone tiles that the wife loves.  This sounds like it's going to have to be a project for 2022, we already have a list a mile long of other stuff to get done.  I was hoping there was a simple way to do it.  Thanks for all the feedback regardless!


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