Insulating under a floor

[ShoulderThingThatGoesUp]

My house was built in 1910, and the laundry room seems to be on a finished former porch. The basement does not go underneath it and there is no crawlspace; the foundation is brick. Because I had some foundation work done last year, I know that there is some space underneath the laundry room, empty except for some antique garbage that somebody threw there once upon a time.

Yesterday the low here was 5 F, and we noticed some ice crystals on the bottom of the kitchen towels, baby bibs, etc hamper we keep in the laundry room. Two problems:
1. There's standing water in that hamper. Not appealing.
2. The floor in the laundry room was literally freezing.

We opened the door to the laundry room immediately - it has heat, but it's the furthest radiator from the furnace - and the ice melted. I know that the pipes are fine because I have a load of laundry going in there now. But I'm obviously pushing dollar bills through the floor of that room.

So, here are my questions:
1. How would it be best to insulate that floor? I am thinking of drilling holes to the space either from the basement or from above, but they would have to be big holes, right?
2. What kind of insulation would be best? Are there fire code concerns with under-floor insulation?
3. Can I DIY it, or should I hire somebody who knows what they're doing?

The floor is sheet vinyl on top of 1910s tract house back porch. There seems to be a trap door under the vinyl.

[workerbee]

Our home was built in 1889, and we had the same problem, porch turned into laundry room. We cut a trap door under the dryer and crawled through that opening and put the thick insulation bats between the floor joist. Then just for good measure we used a thick wire that we zigzag across the joist and stapled them secure so it didn't fall out. Don't forget to insulate the trap door.
You can do it yourself if you are brave, not afraid of spiders (not a problem if it is cold) and not afraid of tight spaces.
Good Luck!

[zolotiyeruki]

My sister lives in a house with a similar problem--poorly-insulated laundry room in a deck-turned-extra-room.  Their approach was to "do it right"--they'll rip the whole thing out, pour a proper foundation, and rebuild it with a proper structure and utilities and insulation.

It depends on where you live, but chances are there's nothing up to code in that room.  That being said, here are a couple thoughts:
1)  You need a vapor barrier in there somewhere, and given your climate, you want the vapor barrier between the room and the cold environment.  So don't just blow insulation in there. 
2)  You *could* just fill the whole space with spray foam, which would address both the vapor barrier and insulation issues at the same time.  Spray foam is relatively expensive, however. How big is the room?
3)  If you could somehow get a vapor barrier attached to the underside of the floor, you could, I suppose, fill the void underneath with cellulose, but I'd be worried about moisture and mold then growing there.

[ShoulderThingThatGoesUp]

I think we're going to end up getting somebody to fill it with expansive foam. It's a 8x6 room, so we're not talking about a lot of space. The entire house was gutted and rebuilt inside in 2011 by professionals, so I'm not worried about plumbing/electrical being OK because all that is from 2011. A demo and rebuilt would not be worth it and would cost a substantial portion of the house's worth.

[nereo]

I'll try tacking onto this tread before starting a new one because my situation is similar.

I  have a completely enclosed porch that was formerly a large balcony (20' x 8'). Due a wall of extremely large single-pane glass windows, it's impractical to keep heated through the cold winter months, and replacing these windows with energy efficient ones would cost several $k.  However, because my upstairs neighbors recently renovated, the ceiling is well insulated, as are 3 out of the 4 walls (all but the exterior wall with the huge-ass single-pane windows).

The floor right now is a plywood subfloor on top of joists with about 6" of vertical space.  Once it warms up I'm going to lay down decking to make finish that room into a 3-season enclosed patio.

My question: Is there any reason NOT to insulate under the floor?  Given the low, low cost of insulation and quick application time it seems like "why the hell not" - if I ever do get the money to replace those giant energy-sucking windows I wouldn't have to rip up the floor.  Am I missing anything?

[going2ER]

Home Depot, and I am certain other hardware stores, sell the spray insulation foam kits which is much cheaper than hiring someone to do it. However,  it needs to be above a certain temperature outside to use it so you may have to wait until spring. We have a rock foundation and we found it to be the most practical and cost effective way for insulating it and it wasn't difficult to use.

[ShoulderThingThatGoesUp]

I'll try tacking onto this tread before starting a new one because my situation is similar.

I  have a completely enclosed porch that was formerly a large balcony (20' x 8'). Due a wall of extremely large single-pane glass windows, it's impractical to keep heated through the cold winter months, and replacing these windows with energy efficient ones would cost several $k.  However, because my upstairs neighbors recently renovated, the ceiling is well insulated, as are 3 out of the 4 walls (all but the exterior wall with the huge-ass single-pane windows).

The floor right now is a plywood subfloor on top of joists with about 6" of vertical space.  Once it warms up I'm going to lay down decking to make finish that room into a 3-season enclosed patio.

My question: Is there any reason NOT to insulate under the floor?  Given the low, low cost of insulation and quick application time it seems like "why the hell not" - if I ever do get the money to replace those giant energy-sucking windows I wouldn't have to rip up the floor.  Am I missing anything?

Hard to see how insulating under the floor wouldn't help. That said, have you tried curtains/blinds on the windows? They might help a surprising amount.

[zolotiyeruki]

I'll try tacking onto this tread before starting a new one because my situation is similar.

I  have a completely enclosed porch that was formerly a large balcony (20' x 8'). Due a wall of extremely large single-pane glass windows, it's impractical to keep heated through the cold winter months, and replacing these windows with energy efficient ones would cost several $k.  However, because my upstairs neighbors recently renovated, the ceiling is well insulated, as are 3 out of the 4 walls (all but the exterior wall with the huge-ass single-pane windows).

The floor right now is a plywood subfloor on top of joists with about 6" of vertical space.  Once it warms up I'm going to lay down decking to make finish that room into a 3-season enclosed patio.

My question: Is there any reason NOT to insulate under the floor?  Given the low, low cost of insulation and quick application time it seems like "why the hell not" - if I ever do get the money to replace those giant energy-sucking windows I wouldn't have to rip up the floor.  Am I missing anything?

The only hesitation I would have would be with regards to condensation and potential mold, if you're going with anything other than spray foam.  Just make sure that if you put in spray foam, you insulate the *entire* underside, so there aren't any holes for moisture to sneak in behind the foam.

On the topic of windows, our home has cheap builder-grade vinyl windows.  Double-paned, but still only about R-2.  I found a cheap way to insulate them, that even passed the wife test.  I got 3/4" styrofoam insulation sheets ($5 each at Menard's), cut them to the size of the window, and covered each with a cheap Walmart fleece blanket ($2.88 ea).  The can of spray adhesive was about $10, and we've made four window covers (each 3' x 5') so far at a total cost of about $35.  Our kids' rooms are noticeably warmer at night now, and because the panels are covered with fabric, they aren't an eyesore.

[nereo]

Hard to see how insulating under the floor wouldn't help. That said, have you tried curtains/blinds on the windows? They might help a surprising amount.

On the topic of windows, our home has cheap builder-grade vinyl windows.  Double-paned, but still only about R-2.  I found a cheap way to insulate them, that even passed the wife test.  I got 3/4" styrofoam insulation sheets ($5 each at Menard's), cut them to the size of the window, and covered each with a cheap Walmart fleece blanket ($2.88 ea).  The can of spray adhesive was about $10, and we've made four window covers (each 3' x 5') so far at a total cost of about $35.  Our kids' rooms are noticeably warmer at night now, and because the panels are covered with fabric, they aren't an eyesore.

Thanks for the thoughts/suggestions about using curtains/blinds/fleece etc.  unfortunately it won't work in my situation.  The windows that are there are single-pane (R~1) and span a space that is 5' x 22'.  Yeah, **huge* heat loss.  Add our Canadian winters (outside temp frequently drops to -20ºF) and we would need to keep the windows covered with blankets/foam 100% of the time in winter. The enclosed patio provides all the light for the kitchen, bedroom and dining room.    Eventually I'll replace those suckers with something closer to an R=4, but as I said it will cost many thousands$$, even if I break up the windows into several more stock-friendly sizes.  C;est la vie.

The only hesitation I would have would be with regards to condensation and potential mold, if you're going with anything other than spray foam.  Just make sure that if you put in spray foam, you insulate the *entire* underside, so there aren't any holes for moisture to sneak in behind the foam.

Good caution about the potential for moisture.  Definitely leaning towards closed-foam since that has the highest R value for the relatively small amount of space available.  Would be a DIY project since I can be as messy as I want in this space since it is still unfinished.

[Bob W]

You can buy cellulose insulation from Home Depot.  They usually rent you the blower for free with a purchase.  So maybe $100?  I wouldn't do expanding foam on a large crawl space with pipes. 

Then you cut two or three proper and out of sight holes.   Blow the cavity full in about 20 minutes, return machine and boom you're don't.

The real question is have you had a whole house energy audit completed?   If not, why not?

Check with your electric company for resources on this.

So the correct answer is blow in cellulose insulation. 

[nereo]

You can buy cellulose insulation from Home Depot.  They usually rent you the blower for free with a purchase.  So maybe $100?  I wouldn't do expanding foam on a large crawl space with pipes. 

There are no pipes or electrical conduits to worry about.  I've been leaning towards the expanding foam because there's only about 6" of vertical space, and it has the (much) higher R value for not a huge increase in price for that volume (especially since I won't be able to buy enough blown-cellulose bags to qualify for the 'free rental' of the blower).  I'd be unscrewing and pulling up the plywood subfloor anyway instead of cutting holes.  There are a few cross-braces which would make insulating diffucult otherwise, and it's a 30 minute job to take lift up the plywood anyway.

The real question is have you had a whole house energy audit completed?   If not, why not?
 

yes, I had a whole-house energy audit completed when I moved in in 2012.  The enclosed patio wasn't included because it's technically outside (it used to be a balcony before it was enclosed, and is exterior of the building wall.  As mentioned before it's not practical to use in the winter until those enormous windows are replaced with energy efficient ones - but since I'll be doing the flooring this spring I figured I might as well insulate the floor BEFORE I put something nice down, just so that years down the road I don't have to pull it all up if/when I get the budget to replace all the windows.
Currently and for the foreseeable future it's a 3-season space, used for dining semi al-fresco and for messy projects.

[ShoulderThingThatGoesUp]

You can buy cellulose insulation from Home Depot.  They usually rent you the blower for free with a purchase.  So maybe $100? I wouldn't do expanding foam on a large crawl space with pipes. 

Then you cut two or three proper and out of sight holes.   Blow the cavity full in about 20 minutes, return machine and boom you're don't.

The real question is have you had a whole house energy audit completed?   If not, why not?

Check with your electric company for resources on this.

So the correct answer is blow in cellulose insulation.

Won't cellulose insulation get moldy? I'm pretty sure the floor of this crawl space is dirt. The crawl space itself has no pipes, I'm pretty sure. The only pipe it might have is a steam pipe for the radiators - so that might be another concern...

I went outside today to put some salt on the walking paths and our sidewalk, so I took a look at the outside of the laundry room. There is some vinyl siding below the laundry room's floor level, and it looks like (but it was freezing rain so I didn't fully investigate) those are just attached to some planks. So if we could cut that out and replace it easily, there would be plenty of access.

[zolotiyeruki]

There are no pipes or electrical conduits to worry about.  I've been leaning towards the expanding foam because there's only about 6" of vertical space, and it has the (much) higher R value for not a huge increase in price for that volume (especially since I won't be able to buy enough blown-cellulose bags to qualify for the 'free rental' of the blower).  I'd be unscrewing and pulling up the plywood subfloor anyway instead of cutting holes.  There are a few cross-braces which would make insulating diffucult otherwise, and it's a 30 minute job to take lift up the plywood anyway.

I didn't realize you plan on pulling up the floor--that opens up an option that may be the best of both worlds:  pull up the floor, and put styrofoam sheet insulation against the ground (to keep water away from the blown-in insulation).  Then fill the space with loose-fill fiberglass or cellulose, or heck, even fiberglass batts, then lay down (and this is important!) a vapor barrier on top of the insulation.  Personally, I'd fill in the joist bays all the way up and lay the vapor barrier on top of the joists, just underneath the plywood subfloor.  Or, you could fill insulation up to the bottom of the joists and run the vapor barrier under the joists instead.

As for reasons why not....well, it's time and money, and if you'll only use it as a 3-season porch, you might not benefit very much from it, since the weather will (hopefully) be tolerable during those three seasons.  Also, if water pools or drains underneath, you'll definitely want to fix that before insulating.

[nereo]

There are no pipes or electrical conduits to worry about.  I've been leaning towards the expanding foam because there's only about 6" of vertical space, and it has the (much) higher R value for not a huge increase in price for that volume (especially since I won't be able to buy enough blown-cellulose bags to qualify for the 'free rental' of the blower).  I'd be unscrewing and pulling up the plywood subfloor anyway instead of cutting holes.  There are a few cross-braces which would make insulating diffucult otherwise, and it's a 30 minute job to take lift up the plywood anyway.

I didn't realize you plan on pulling up the floor--that opens up an option that may be the best of both worlds:  pull up the floor, and put styrofoam sheet insulation against the ground (to keep water away from the blown-in insulation).  Then fill the space with loose-fill fiberglass or cellulose, or heck, even fiberglass batts, then lay down (and this is important!) a vapor barrier on top of the insulation.  Personally, I'd fill in the joist bays all the way up and lay the vapor barrier on top of the joists, just underneath the plywood subfloor.  Or, you could fill insulation up to the bottom of the joists and run the vapor barrier under the joists instead.

As for reasons why not....well, it's time and money, and if you'll only use it as a 3-season porch, you might not benefit very much from it, since the weather will (hopefully) be tolerable during those three seasons.  Also, if water pools or drains underneath, you'll definitely want to fix that before insulating.

Ok - a bit of explaining what I'm dealing with.  My enclosed porch was originally a balcony, and the flooring was originally a wooden deck with an open crawl-space underneath (enclosed and protected from the weather now, but completely uninsulated).  For reasons I can't fathom it was originally a step down from inside the house. When it was renovated in 2011 the builder basically added a gridwork of 2x6" to raise the floor up to be at the same level as the interior, and then put 3/4" ply on top of that as the new subfloor.   That's why there's this 5-6" uninsulated dead-space under the plywood subfloor and the original decking.  Does that make sense?

So in terms of insulating I really have two options and could utilize either or both of them.  I could apply insulation from underneath from the crawl-space, and/or I could put insulation under the plywood floor.  Since I'll be putting down a flooring in the spring, there will be nothing else in that room.  The plywood subfloor is affixed with screws and it would take me ~30 minutes to lift it all up - I'm estimating insulating would be at most a half-day job.  But once I lay the final flooring down I loose this option.  Hence my thought process of "any reason (other than a few hundred$ and a half-days' work) not to do it..." - it will either be then or never.

My main questions/concerns now is how to think of the moisture barrier.  since moisture could potentially enter and/or escape through both the top and the bottom, where should I put the barrier(s)?  Do I need two (one on the bottom and one on the top)? 
Thanks!

[QajakBoy]

You wouldn't want two moisture barriers because it could become a moisture trap if moisture ever got in between.
It seems to me that you would want to put a moisture/vapor barrier on the soil side since the soil is the likely moisture source.

[aj_yooper]

Wouldn't you need a vapor barrier on the earth too?  And, get the debris out of the space as they often grow stuff.

[nereo]

You wouldn't want two moisture barriers because it could become a moisture trap if moisture ever got in between.
It seems to me that you would want to put a moisture/vapor barrier on the soil side since the soil is the likely moisture source.

There is no "soil side".  Underneath the floor of my enclosed patio is a storage space (which has its own wood floor, but isn't insulated).
My enclosed patio is 5-8' off the ground (it's on a slope - one end of my home is at ground level while patio is at the far end and at the extreme end it is 8' off the ground.)  Underneath the enclosed patio is another enclosed (completely protected from weather) but completely uninsulated space.

[Bob W]

You can buy cellulose insulation from Home Depot.  They usually rent you the blower for free with a purchase.  So maybe $100?  I wouldn't do expanding foam on a large crawl space with pipes. 

There are no pipes or electrical conduits to worry about.  I've been leaning towards the expanding foam because there's only about 6" of vertical space, and it has the (much) higher R value for not a huge increase in price for that volume (especially since I won't be able to buy enough blown-cellulose bags to qualify for the 'free rental' of the blower).  I'd be unscrewing and pulling up the plywood subfloor anyway instead of cutting holes.  There are a few cross-braces which would make insulating diffucult otherwise, and it's a 30 minute job to take lift up the plywood anyway.

The real question is have you had a whole house energy audit completed?   If not, why not?
 

yes, I had a whole-house energy audit completed when I moved in in 2012.  The enclosed patio wasn't included because it's technically outside (it used to be a balcony before it was enclosed, and is exterior of the building wall.  As mentioned before it's not practical to use in the winter until those enormous windows are replaced with energy efficient ones - but since I'll be doing the flooring this spring I figured I might as well insulate the floor BEFORE I put something nice down, just so that years down the road I don't have to pull it all up if/when I get the budget to replace all the windows.
Currently and for the foreseeable future it's a 3-season space, used for dining semi al-fresco and for messy projects.

Good for you on the energy audit!!!!

I really think that is the step that every MMMer should take.

I either missed or neglected that the area cavity was so small and without pipes.  So by all means expandable foam away my friend.

Let us know how it turns out.   Best of luck!

[zolotiyeruki]

Ok - a bit of explaining what I'm dealing with.  My enclosed porch was originally a balcony, and the flooring was originally a wooden deck with an open crawl-space underneath (enclosed and protected from the weather now, but completely uninsulated).  For reasons I can't fathom it was originally a step down from inside the house. When it was renovated in 2011 the builder basically added a gridwork of 2x6" to raise the floor up to be at the same level as the interior, and then put 3/4" ply on top of that as the new subfloor.   That's why there's this 5-6" uninsulated dead-space under the plywood subfloor and the original decking.  Does that make sense?

So in terms of insulating I really have two options and could utilize either or both of them.  I could apply insulation from underneath from the crawl-space, and/or I could put insulation under the plywood floor.  Since I'll be putting down a flooring in the spring, there will be nothing else in that room.  The plywood subfloor is affixed with screws and it would take me ~30 minutes to lift it all up - I'm estimating insulating would be at most a half-day job.  But once I lay the final flooring down I loose this option.  Hence my thought process of "any reason (other than a few hundred$ and a half-days' work) not to do it..." - it will either be then or never.

My main questions/concerns now is how to think of the moisture barrier.  since moisture could potentially enter and/or escape through both the top and the bottom, where should I put the barrier(s)?  Do I need two (one on the bottom and one on the top)? 
Thanks!

Ah, that makes it *much* clearer!  Thanks for taking the time to explain.  This slightly changes what I'd suggest.  Here's my current suggestion:  Pull up the subfloor.  Fill the voids (on top of old decking) with fiberglass batts. Lay a vapor barrier on top of it all, then screw down the subfloor.  Cheap, fast, and you get R-19.  Spray foam will get you a better r-value and better sealing, but it's more expensive and messier to install.

The rule of thumb for vapor barriers is "put it on the warmer side of the insulation".  That way, the moisture in the warm air doesn't meet the cold, and doesn't condense.  By comparison, if you put the vapor barrier on the *cold* side of the insulation, the moisture will travel through the insulation until it hits the (cold) vapor barrier, then condenses, and you end up with mold issues.  QajakBoy is right about two vapor barriers--that's a no-no, as it creates a "moisture sandwich", which is a recipe for mold.  Closed-cell foam avoids the whole issue, since it's a vapor barrier throughout. 

Alright, as I'm typing I'm coming up with more thoughts (your description really spurred some creativity).  Here's another idea:
1)  pull up subfloor
2)  lay down vapor barrier
3)  reinstall subfloor
4)  fill the voids between old and new decking with cellulose (cut holes from underneath).  This will give you the good sealing properties of the spray foam and the cheapness of blown-in insulation
Optional 5)  install batts between the old, lower joists.  And enjoy your nice, warm floors.

[nereo]

Ah, that makes it *much* clearer!  Thanks for taking the time to explain.  This slightly changes what I'd suggest.  Here's my current suggestion:  Pull up the subfloor.  Fill the voids (on top of old decking) with fiberglass batts. Lay a vapor barrier on top of it all, then screw down the subfloor.  Cheap, fast, and you get R-19.  Spray foam will get you a better r-value and better sealing, but it's more expensive and messier to install.

The rule of thumb for vapor barriers is "put it on the warmer side of the insulation".  That way, the moisture in the warm air doesn't meet the cold, and doesn't condense.  By comparison, if you put the vapor barrier on the *cold* side of the insulation, the moisture will travel through the insulation until it hits the (cold) vapor barrier, then condenses, and you end up with mold issues.  QajakBoy is right about two vapor barriers--that's a no-no, as it creates a "moisture sandwich", which is a recipe for mold.  Closed-cell foam avoids the whole issue, since it's a vapor barrier throughout. 

Thanks - !  Thinking about it I think fiberglass batts on top of the old decking will be the way to go, with a vapor barrier on top.  It will insulate the floors well enough for my purposes, and if necessary I could always insulate below the original decking later on.  Plus, it's lower mess than the foam and it will save me from having to rent the blower for blown-cellulose (since i'll only need ~50cf).
Double-bonus, I can put batts in at any temperature, so if I get stir crazy I can start next month.

[ShoulderThingThatGoesUp]

nereo, your situation is leading to me seeing some helpful advice for if I ever decide to fix up the second story of the porch in question, which isn't finished and has a painted copper floor. Thanks for joining in!

[MsAligned]

I have a similar situation 12'x25'x18" from former cement patio to bottom of floor joists so I have been doing a lot of reading and pondering. I recommend these sites for discussion of possible solutions. I have found these sites to be very informative on insulation issues
http://www.greenbuildingadvisor.com/blogs/dept/musings/building-unvented-crawl-space
http://www.finehomebuilding.com/item/17322/whats-the-best-way-of-insulating-a-crawl-space
http://www.thisoldhouse.com/toh/skill-builder/0,,203776,00.html

[ShoulderThingThatGoesUp]

I ended up paying somebody to do this because I thought there might be heating pipes or big problems underneath. Turns out the only thing there was a bunch of scrap wood. However, it no longer hurts to walk in the laundry room. Payback won't be as fast as if I DIYed, but trying to just pump in cellulose would have been a moldy, pointless disaster.

[zolotiyeruki]

I ended up paying somebody to do this because I thought there might be heating pipes or big problems underneath. Turns out the only thing there was a bunch of scrap wood. However, it no longer hurts to walk in the laundry room. Payback won't be as fast as if I DIYed, but trying to just pump in cellulose would have been a moldy, pointless disaster.

What approach did you end up pursuing?  Spray foam on the underside?

[ShoulderThingThatGoesUp]

Sealed it with taping and then faced fiberglass batts (facing up against the subfloor) in between the joists, then more batts around the walls of the space. Still some air ventilation underneath, which is fine as it's a dirt-floor crawlspace, but on cold days like today it no longer hurts to walk in those rooms when you have socks on.

[PatStab]

I hope you didn't leave the wood laying on the ground under there, termites will love that.  We bought an old 1910 house for a rental.  It will take a year to redo it as hubby is only home periodically.  We have a porch area like that but maybe 6 X 6 or less, you can see under there and see outside between some of the foundation.  We are going to reseal all that from the outside.  There were termites under there, I had it all treated.  It too was a porch and the laundry room will be out there.  We may have to do the foam insulation out there too, no good way to do it otherwise. But we have a basement, we are going to put under floor batt insulation and keep it up with chicken wire.  We are going to do blown in insulation in the attic after hubby finishes the new wiring up there.  Then drill holes in the interior drywall and blow insulation in.  We don't want to put those plugs all over outside in the aluminum siding.

I am refinishing all the old windows, inside and out and reputtying them, also putting in new ropes on the weights.  It has storm windows and I'm sealing them.

The house should be good and warm when we are done, that helps renters to pay their rent if it doesn't all go for utilities.

[ShoulderThingThatGoesUp]

Nope, cut up the wood and gave it to a friend's grandfather who heats with wood.