Flooring and insulation question for the contractor types

My wee little house currently has carpet everywhere except the kitchen and bathroom.  It is 8 year old jobber junk carpet and something needs to be done.

I envision keeping the carpet in the bedrooms as it doesn't show much wear, but at least the living room and hallway needs something to be done.  I could re-carpet, but I do love the look and ease of cleaning that comes with a hard floor.  Being a 1920s build, there is a tiny basement, but most of the house is over a dirt crawlspace.  T&G subfloor with no insulation.  There is sheet plastic on the dirt in the crawlspaces as a sorta vapor barrier.

I would love to insulate the floor, but I would need a 5-year-old to get in that crawlspace.  It is really only about 12" tall.  I could rip up the T&G and do OSB and do the work from the top, but from looking at the joists, it's obvious they installed them knowing it was strips of T&G, not keeping them accurately spaced.  That would mean a lot of additional scabs of lumber at joints.

What would you contractors do?  As I see it, my choices:

1. rip out T&G from the top, hang vapor barrier under the joists, and lay insulation in it, then lay over with OSB.
2. find a really skinny person who likes spiders to go under and do it from the bottom, then lay luan to span any soft spots and hardwood or plank flooring on top.
3. skip the insulation and just put down new carpet.

The big part is, I don't want to add any thickness to the floor.  My ceilings are only 84" as it is.  I don't want them to be any shorter.

Blow-in insulating into crawlspace, insulating - high-R value underlayment, flooring of your choice?

pheller said:

Blow-in insulating into crawlspace, insulating - high-R value underlayment, flooring of your choice?

Blown-in on top of dirt/plastic?  Never thought about that.  I assumed it would have to be up off the vapor barrier and dirt.

Spray foam?

12"?  Plenty of room to get in there. Not that it'll be fun. 

It sounds similar to my house. Half the living space is over the basement, the other half over a crawl space with plastic covering dirt. The basement is not effectively partitioned from the crawl space. Because of that, I have never felt trying to insulate the floors would be all that effective. There are so many other parts of the house that need better insulation before the floors.

Spray foam.  I'd talk to a local company and ask what they can manage for access. 

Curtis said:

pheller said:

Blow-in insulating into crawlspace, insulating - high-R value underlayment, flooring of your choice?

Blown-in on top of dirt/plastic?  Never thought about that.  I assumed it would have to be up off the vapor barrier and dirt.

That doesn't sound like a good idea.  It's just a huge critter nest.

I don't think he meant loose fill blown-in.  I'm assuming he meant something like cellulose blown-in (which would stick to the bottom of the joists and decking).  But I don't think that would work either... 12" may be to tight an area to run the equipment in.

I think your best solution is gonna be 6" fiberglass batts and a couple of Mexicans.

If you put blown-in insulation on the ground on top of the vapor barrier it will be a disaster.

The vapor barrier will be on the wrong side of the insulation.  You are in a cold region.  That means moisture from the warm side of the insulation (the living space) will condensate IN the insulation.  It will be soaking wet, and an easy target for termites, and all kinds of vermin.

SVreX said:

If you put blown-in insulation on the ground on top of the vapor barrier it will be a disaster.

The vapor barrier will be on the wrong side of the insulation.  You are in a cold region.  That means moisture from the warm side of the insulation (the living space) will condensate IN the insulation.  It will be soaking wet, and an easy target for termites, and all kinds of vermin.

That's one thing I never understood... which way the vapor barrier goes for different applications.  So, it I were to pull up the subfloor, I would install a batt just like I would in the wall.... paper up? Then support the bottom with strings or 1x lumber instead of plastic?

I could see the spray on stuff as opposed to the blown in stuff.

Long term, I'd love to concrete the crawlspace, which would be much easier if the subfloor is out.  I think if I have the subfloor out, I should take that opportunity but that will require pros.  I'm not going to make assumptions I know how to modify the foundation of a house.

My parents' crawl space is about 22" tall.  We put down thick plastic sheet on the dirt floor; you leave there cleaner but I like to think T beat back some moisture.

Floor joices are 16" on center so we cut 2" blue styrofoam to 14" strips and pinned it to the floors above using metal strips to hold it up.

Can't swear it's better, buy it can't make it worse.

Cloustrophobic?  Find a hungry pack of college kids.

Tip:  Insulate the living space.  Look at your attic, roof is not insulated.

Curtis said:

SVreX said:

If you put blown-in insulation on the ground on top of the vapor barrier it will be a disaster.

The vapor barrier will be on the wrong side of the insulation.  You are in a cold region.  That means moisture from the warm side of the insulation (the living space) will condensate IN the insulation.  It will be soaking wet, and an easy target for termites, and all kinds of vermin.

That's one thing I never understood... which way the vapor barrier goes for different applications.  So, it I were to pull up the subfloor, I would install a batt just like I would in the wall.... paper up? Then support the bottom with strings or 1x lumber instead of plastic?

Yes. That is correct. 

You wont like the price of the spray on stuff. 

In reply to Curtis :

I’m going back to your original question...

1920’s vintage house in PA. 

First off, it’s highly unlikely your floor insulation contributes much to the discomfort of energy efficiency of your house. If it was perfectly insulated in accordance with modern energy standards, it would probably impact your energy bill less than 5%. I’d bet less than 2%. And you wouldn’t feel the difference. 

That’s because your primary inefficiencies are your roof, your walls, your heating unit, and your windows. Your primary discomfort is not thermal performance. It’s air infiltration (that means it’s a drafty old house). 

Therefore, you ABSOLUTELY DO NOT want to consider tearing up the tongue and groove subfloor, under any circumstance. You will be making a mess of the structural integrity of the house (the walls are sitting on the subfloor). The gains you will have are almost immeasurable, and the problems you create will be monumental. 

My suggestion is you address air infiltration, and don’t worry about the thermal performance. Pull up the carpets, add a air infiltration underpayment barrier, seal the joints, caulk where the underpayment meets the walls, and reinstall the carpet. Then add insulting rings at all of your electrical outlets and switches  

You will see a noticeable improvement if you address air infiltration. 

Improving thermal performance will cost a lot of money, and give you negligible noticeable improvements. 

The general rule of thumb is that the vapor barrier goes next to the living space.  However, in dirt crawl spaces I've done sheet plastic on the dirt, to reduce the moisture in the crawl space and make working under there slightly less unpleasant.  I'd do that, with fiberglass batts up inside the joists. I like to us chicken wire to hold it in place.  Well, maybe not like.  It's a pain to install.  It's more accurate to say that I've found it to be effective.

I'm not a pro builder but I've worked on a bunch of old trailers and farmhouses in North Central Maine working with Volunteers in Mission and that's the method that we found struck the best balance between cost and effectiveness.  The most effective is spray foam but I suspect that the price will make you want to explore other options.

Glad I asked before I got out the crow bar.  I helped with a subfloor project before and we just basically cut the T&G as close to the wall as we could with a circular saw, then furred out the sill, and laid in OSB.  It was a pain, but it was also on a 1950s house that had water/mold damage so it needed to happen.  I was also not in charge of that project, I just ran the saw.

My main concern with replacing the carpet with hardwood or plank was that the wee bit of R-value of the carpet and padding would be lost and my floor would be cold.  I suppose I could mitigate that problem by wearing socks or using area rugs, but I wondered how much it would actually allow radiant and conducted heat out of the room.  The barrier you suggest putting under the floor would mostly solve the convection loss.

I thought about some kind of radiant floor heat, but that seems counter-productive... just spending energy to put back energy I'm losing.  I don't want to add heating because I'm creating a heat loss situation.

Socks are much cheaper than radiant heat. 

Yes you are right. The carpet is helping your comfort level. 

It’s probably also full of every conceivable form of dirt and nastiness. 

If I was Curtis, here’s what I would do...

I’d sacrifice 1 1/2” of ceiling height, and add insulation and plywood to the top of the subfloor. 

3/4” Dowboard will give you about R-3.5. That’s not much, but it’s better than nothing. The Dowboard will also act as an excellent air infiltration barrier, AND vapor barrier. It will seal all those joints in the T&S subfloor. Tape the joints, caulk the crap out of everything. 

Then, I would install 5/8” subfloor plywood on top of the Dowboard. Stagger the joints. Screw the plywood to the T&G, sandwiching the Dowboard in between. Then caulk the plywood joints, and all of the screw holes. Cover with the finished flooring of your choice. 

You’d have a nice tight floor, much more comfortable, and you could do it 1 room at a time. DIY. 

Radiant heat is awesome!  After having it I'll never install a bathroom floor in a house I live in without it.  If I still lived in Upstate NY I'd never put in any non-carpet floor without it in any room.

This has been an interesting read, and somewhat relevant to me given I'm about to relay t&g over a low clearance dirt crawl space.

I've been weighing up subfloor insulation, but cost vs benefit and potential for issues means I'll most likely forego it. I was planning on concentrating on minimising air leaks, and this thread has pretty much confirmed that that'll give me the best bang for my buck.

Climate wise, I don't think there's ever been a recorded temperature lower than 20f in the area, and really there's only a handful of nights where the temp will drop below 30. 

Because I want exposed timber floors, I'll be looking at taping or slivering the joints between boards and caulking or inserting a foam expansion joint between the boards and wall (double brick home with suspended floors) and then caulking between the skirting boad and floor.

You could always try removing the carpet and concentrating on stopping air leaks first and see how comfortable/uncomfortable it is and then go from there. Svrex's suggestion of sacrificing a little bit of ceiling height is a good one if the t&g floor alone proves to be to cold.

In reply to Curtis :

meth heads are skinny.  How do you think they get those catalytic converters off?  

While I agree that I could sacrifice height, I just refuse.  I would rather do the crawlspace shuffle than lose one of my precious 84" of height.  As it is, I have to duck to go through my interior doorways.  I won't make it worse.

So, from your suggestions, I might go with a vapor/air barrier on the T&G, then some 5mm underlayment, then whatever flooring I choose.  If I do carpet, I'm sure I'll be ok.  If I do a laminate or plank and it's too cold on my delicate feet, I'll do area rugs.  If that doesn't do the trick, maybe I'll cozy up with the spiders and throw some batts under the subfloor.

How about this crazy idea:  The forced air furnace is in the basement and has no registers down there.  The basement stays moderate simply because the furnace is down there and it's underground.  For instance right now it's about 30 outside, 70 inside, and I'd guess 55-60 in the basement.  How much energy stupidity would it be to cut a small (maybe 4x10") register in the duct down there?  I guess I'm thinking the warm air would rise to under the subfloor.  Some would sneak out the foundation wall, but would it be so much that I'm wasting heat?  My brain says heat rises, and aside from what soaks out the sill and foundation, a large portion of it should make it into the living space?  The air return comes from the main level, so there isn't air being mixed down there, I would just be adding a trickle of hot air that should float up.

And, yes... more insulation in the attic is definitely in the works.  The nice thing is, I don't have soffit vents so I can go nuts with blown-in if I want.  It has gable vents, and when it needs a new roof (likely 5 years or so) I'll add a ridge vent.

In reply to Curtis :

You’re assuming your crawlspace doesn’t leak any air!  Haha!!

Svrex is right. Work on air infiltration first.  Seal up the windows and those stupid insulation packs for electrical outlets work wonders.  Make a huge difference.  

Vapor barrier on top of the subfloor won’t do much. Your gonna fill it full of holes when you nail down your underlayment. 

Note on the ceiling height... my suggestion of 3/4” insulation plus 5/8” of plywood is about equivalent to what you have in carpet and padding.