Insulation suggestions wanted

[tthurman]

A few years ago I added a layer of R-25 to our attic and it has made a dramatic difference. In the coming months I am going to re-insulate our vented crawl space.

Our crawl space is at the lowest a little over four feet and at the highest point around six and a half feet. The joists have metal cross bracing and the builder installed faced R-13 but instead of having the facing flat against the bottom of the sub-floor they simply hopped over the cross bracing. From what I've read this is not ideal and the facing should be tight against the sub floor so I plan to correct this and then fill the remaining cavity with additional unfaced insulation.

One of my concerns is that I installed 3/4" hardwood several years ago on 75% of the first floor. Due to this there are numerous cleats sticking out of the bottom of the sub-floor.

Is there a work around to this or should I not worry if the facing is punctured? I did use 30lb roofing felt on top of the sub-floor while installing the floor and sealed all the seams with duct tape.

Opinions/suggestions would be appreciated.

[adamdivine]

do not worry about puncturing the facing, it is much more important to fill in those gaps. The gaps are effectively killing the R rating for you floor. You may also want to consider a reflective barrier in addition to the insulation. Just make sure you laeave an airspace around the reflective barrier to prevent condensation build-up. If you look to get any input from local contractors, avoid the generic heating/cooling guys and go with someone who specializes in energy efficient heating systems and insulation (i.e., geothermal/solar installers). I have found out the hard way that they know a lot more about the proper way to insulate a house.

By the way, the best thing that you did was spend extra time sealing the gaps in your floor. Air infiltration will cost you more than a lack of R value everytime. Good luck!

[dvenardos]

Can you blow in cellulose? It can go over existing installation.

http://www.cellulose.org/HomeOwners/FAQ.php

[django1]

Are you insulating to keep the cold or the heat out? What type of climate? Knox Vegas?

[rsa]

Opinions/suggestions would be appreciated.

You need to do serious, targeted research before you start. Crawlspace paradigms have changed. The current strategy is to use an unvented, conditioned crawlspace.

Here's a place to start, New Light in Crawlspaces. It also addresses floor joist insulation for those who "insist on doing the vented crawlspace thing".

In general, look for articles by Joe/Joseph Lstiburek. Building Science Corporation is a good reference source as is Green Building Advisor.

[django1]

You need to do serious, targeted research before you start. Crawlspace paradigms have changed. The current strategy is to use an unvented, conditioned crawlspace.

Here's a place to start, New Light in Crawlspaces. It also addresses floor joist insulation for those who "insist on doing the vented crawlspace thing".

In general, look for articles by Joe/Joseph Lstiburek. Building Science Corporation is a good reference source as is Green Building Advisor.

New Light on Crawlspaces is a good article. I like the idea of killing the venting and insulating the outside walls. This always seemed logical to me.

Alternately I like the foil faced isocyanurate under the framing. This could be easy for diy if the underside is obstacle free. That stuff is easy to cut. And you could leave the fiberglass where it is. The sheets are big though, you need a big a access.

[ben9732]

Building Science posts a lot of good info. Agreed about the Iso under the joists and I may pull down my garage ceiling to do that under the bedrooms. Of course now under the new codes I have reinstall 2 layers of 5/8" drywall to the ceiling!

Stephen brings up a good point about access for the Iso boards, but another option is to rip it to joist center lines (if the access is limited to that), attached it to the joists and use a lot of aluminum foil tape to bridge the gaps.

[tthurman]

Are you insulating to keep the cold or the heat out? What type of climate? Knox Vegas?

Ideally to become more energy efficient overall. Knoxville in East Tennessee and according to what I was reading we should have R 30 -38 in the floors.

Thanks for all the input here, I figured I would get some great feedback but this has cast a new light on things for me. I started researching the reflective barrier product after reading adamdivine's response. It is interesting but putting it up could be difficult, especially to achieve complete coverage.

I am really fighting a couple of problems that need to be addressed. When we bought this house it wasn't disclosed that it was plumbed with polybutylene. Since all the visible plumbing was brass and copper there was really no reason for me to think it was anything but copper and I was unaware of PB at that time. If you don't know what this stuff is then consider yourself lucky!

Anyway it was covered in a class action lawsuit and has since been replaced with mid grade copper. Plumbing in the crawl space wasn't insulated as it wasn't "required" per the class action. That said all the plumbing will be getting rubber pipe insulation put on at the same time any additional insulating is done from the joists up.

From reading the article RSA linked it would seem my best bet would be to simply straighten out the insulation I currently have by cutting it at the joist bridging as at these points it drops below the joist itself. Then hang it lower in the joist to create the air space between the existing insulation's vapor barrier and the bottom of the sub floor. This shouldn't be to difficult as it is only R-13 and is considerably smaller than the joist cavities. From this point install the reflective barrier with as much coverage as possible. Wouldn't this effectively create a second vapor barrier? I thought that was a no no.

FWIW, our crawl space is vented but I believe overall it is pretty dry. For other reasons I won't bore you all with I have two standard box fans running in the crawl space. When I had Termidor put in a few years ago the contractor recommended I keep them running and "forget those crawl space vents" so they have been on for years now. I check my crawl space frequently for visible issues....condensation especially and I haven't noticed anything visibly.

[ben9732]

Two vapor barriers as you summize is a bad idea. Yet the R13 is pretty light for that situation. You could pull down the R13 and replace it with unfaced RXX (depending on the joist height – air gap, or it’s easy to remove the kraft paper and add another layer of R11 or R13 unfaced.

[tthurman]

So the radiant barrier is in effect a vapor barrier? I've always found it odd that when I was installing hardwood the recommendation was to use roofing felt as it served as a vapor barrier. This seems like doubling up itself, a vapor barrier on top and then one below on the insulation effectively sandwiching the plywood sub-floor. What's the difference?

I would rather use what I currently have as opposed to investing into more insulation and radiant barrier. I've pulled the kraft paper off before and while it is easy it's damn messy, especially in an enclosed area like the crawl space.

[ben9732]

We are getting into opinions area, and like with insulation, I think the concepts of what we do are changing. In ten years the thoughts posted n Building Science may be declared wrong too.

Other then poly-e or aluminum foil, I don’t consider many things to be a true vapor barrier, more of a vapor retarder, reducing moisture migration from below the floor system, allowing the wood flooring to acclimate gradually. Rosin and tar paper to me are vapor retarders, and their characteristics are related to when the product was made and with what.

If you pull old tar paper from a few decades back you can find it a gooey mess stuck to the underlayment or old floor. The newer stuff doesn’t seem to do this, which I think is a change in the amount of petroleum in the product. Many still use felt/tar paper under floors, but others use rosin paper or the newer AquaBar. I’ve seen old rosen paper under hardwood fine and I’ve seen it turn into powder.

Tar paper / felt I think many years ago was a good products, but I believe like the insulation article above, was thought of from a time when insulation under floors was not a prevalent. And as a secondary use, prevented squeaks when layers rubbed during deflection. Rosin paper does this too, and even when the paper disintegrates, the rosin is left behind to provide the same lubrication.

Anyway as I stated in the paragraph above, the idea is to slowly allow the moisture to dissipate though the flooring, even with a finish on top.

As you noted, the common understanding is to put the insulation vapor barrier (retarder) on the warm side. That view seems to be changing based on the Building Science article referenced at least for certain conditions.

[django1]

Recently I did a job where the clients had a crawl space dug out and made into a basement. The spaces in between the planks of the wood floor on the first floor opened up over the first year. At first the client thought it was from movement from having the building excavated and having new foundations. I rather think that it is because we changed the condition of the air underneath the floor. It went from semi-heated and humid to dry and heated in the winter and less humid in summer. The flooring dried out.

My point is that a little humidity is not necessarily a bad thing.

I know this isn't much help. Do a little research. You know the conditions in your house. Try a well informed compromise. Avoid doing something really bad. I regularly work on old houses (75 or 100 years old) and none of them are done even remotely up to modern code and standards. They are doing just fine...

[ben9732]

....... I regularly work on old houses (75 or 100 years old) and none of them are done even remotely up to modern code and standards. They are doing just fine...

We have a farm house that was built around 1775. American white cedar logs of 5" to 6" diameter for joists, piers and foundation of sandstone with lime mortar, and I really don't want to tell you what else.

The 24' square shed / garage was built in 1958 with 2x3 walls, 2x6 rafters, and two 2x10 across the center to keep the walls from bowing out, open on one side.

Both have handled hurricanes that have come up the coast and countless nor'easters. Builders who get hammered by codes just look at the construction and can't believe they are still standing. Although our last electrician could not believe how hard the cedar framing was in the house when he did some re-wiring. Old growth wood has it's strengths.

[django1]

Sounds like a nice place. I know I wouldn't trade a house like yours for a McMansion...

BTW have you ever seen the tv show Holmes on Homes? He would gut every house I ever worked on and start over from scratch. He does nice work but I wouldn't let him anywhere near my house if I was footing the bill...

[tthurman]

We are getting into opinions area, and like with insulation, I think the concepts of what we do are changing. In ten years the thoughts posted n Building Science may be declared wrong too.

Yeah...that thought entered into my mind as well. I've been doing a great deal of reading since I posted this thread including coming back to this one several times. I really appreciate everyone's input.

After taking everything into consideration I believe I am going with my original plan. Adding enough R-XX insulation to get me where I need is substantially more achievable than putting in the radiant barrier. There is just too much crap in the way to put this up.

My neighbor had put in hardwood flooring and noticed from winter to summer he was getting cupping. He hired a contractor that came out and replaced the plastic that is commonly used in crawl spaces with a very thick heavy duty material. This stuff was white and about 1/16 thick. It was complete floor coverage and about 3 - 4 feet on on the walls and support columns. I'm not sure moisture was his problem but if it was I'd say he solved it.

Long story short, I believe adding insulation as I originally planned following up with replacing my plastic with a superior product such as the above mentioned, is how I will go. I'll keep my crawl space vents closed and see how it goes and perhaps get a dehumidifier for the humid spring/summer seasons.