# Thread: Space between insulation and sub floor

1. ## Space between insulation and sub floor

There is about a 4 inch gap between the insulation and sub floor. This is located in a vented crawl space. I thought this was a pretty simple issue, but the insulation contractor says it is fine. Do you report this?

2. ## Re: Space between insulation and sub floor

Originally Posted by mathew stouffer
There is about a 4 inch gap between the insulation and sub floor. This is located in a vented crawl space. I thought this was a pretty simple issue, but the insulation contractor says it is fine. Do you report this?
I don't see a reflective barrier indicating required space for staple up under subfloor radiant heat so yes. I also don't see a perm barrier or kraft on the warm side.

I see nothing as far as a thermal break between the lower flange of the PRIs and the exposed climate via the ventillated crawl space. The tremendous void shown will ventilate the joist bay quite effectively, negating the R value and creating a vent chute via the subfloor.

I also see pex down under the insulated thermal envelope. Although PEX might be more freeze resistant than other plumbing - it isn't freeze proof, and you're doing the energy efficiency of the hot water system (and plumbing system in general) no favor having it exposed and outside the thermal envelope in a ventilated crawl.

I see batt (crammed) up against porous cement outside crawl wall (Left side of photo) with no barier/liner. Wet compressed spun insulation is nearly worthless as far as R value.

Finally I see smaller ga. Romex stapled up on the underside (flange) of the PRIs in a crawl space - Not allowed. Only one set larger ga. allowed otherwise must be up within (See exposed work) and protected. If that's NM-B not NMC-B also NG in unfinished, unconditioned crawl.

Last edited by H.G. Watson, Sr.; 12-13-2009 at 02:51 PM.

3. ## Re: Space between insulation and sub floor

Mathew,

The simple answer to your question is . . . If the insulation is not in contact with the subfloor it is not able to provide its potential insulating value. If there is a large enough void between the subfloor and the insulation convective loops may form.

Last edited by Bruce Breedlove; 12-13-2009 at 03:35 PM. Reason: spelling

4. ## Re: Space between insulation and sub floor

Originally Posted by mathew stouffer
There is about a 4 inch gap between the insulation and sub floor. This is located in a vented crawl space. I thought this was a pretty simple issue, but the insulation contractor says it is fine. Do you report this?
Mat,

It is a simple issue, that being that the insulation contractor did not install the insulation properly and he knows he will lose money having to go back and do it properly.

From the 2006 IRC. (bold and underlining are mine)
- N1102.2.5 Floors. Floor insulation shall be installed to maintain permanent contact with the underside of the subfloor decking.

Also, as H.G. noted, that PEX is outside the thermal envelope and is not protected from freezing. H.G. also pointed out that large gap in the insulation ... which virtually negates the insulation being installed.

5. ## Re: Space between insulation and sub floor

Yeah I pulled a piece out so we could see the space above the insulation. Thanks for all the info guys.

6. ## Re: Space between insulation and sub floor

Originally Posted by Bruce Breedlove
Mathew,
If there is a large enough void between the subfloor and the insulation convective loops may form.

I also see pex down under the insulated thermal envelope.
I'm assuming this is regional and not code. This is the case with every crawlspace here........I can think of no exceptions.

7. ## Re: Space between insulation and sub floor

not sure what size your TJ I are but the insulation should be the same thickness ,,but say your joist,{tji} are 11/7/8 and you use r-19 and the batts settle to string support your gonna have a gap,,its not a proplem as long as batts are tight between joist and any voids are filled.You could always do asimple test,,put some r-13 in one bay and do a temperture comparison with the other bay.,or have the contractor come back and push it up tight and held in place with flex support rods,,very simple fix,,why he didnt to that in the first place and then run a string to support is beyond me.Also unfaced batts in crawl is pretty standard proceedure as long as you have a ground vapor barrier in place,,check with local code on exposed romex,if you can run on top of rafter cord then you should be able to run to bottom of floor joist ,,and unless you have hydrostatic pressure that insulation should be fine between concrete and joist,,pretty simple thing to check and follow up if it does show signs of moisture .did you have heated floor system ?? i didnt see anything

8. ## Re: Space between insulation and sub floor

"I also see pex down under the insulated thermal envelope."

Originally Posted by chris mcintyre
I'm assuming this is regional and not code.
It is code ... the IRC and probably any other plumbing code.

This is the case with every crawlspace here........I can think of no exceptions.
You and most everyone else too ... that is probably one of the most often violated section of the code - seems that almost no AHJ enforces that until it is brought to their attention, and some need it brought to their attention many times before they will enforce it ... and others simply ignore it.

From the IRC.
- P2603.6 Freezing. In localities having a winter design temperature of 32°F (0°C) or lower as shown in Table R301.2(1) of this code, a water, soil or waste pipe shall not be installed outside of a building, in exterior walls, in attics or crawl spaces, or in any other place subjected to freezing temperature unless adequate provision is made to protect it from freezing by insulation or heat or both. Water service pipe shall be installed not less than 12 inches (305 mm) deep and not less than 6 inches (152 mm) below the frost line.

You get the "winter design temperature" from Appendix D in the IPC. Table R301.2(1), under Winter Design Temp e, at not e, states:
e. The outdoor design dry-bulb temperature shall be selected from the columns of 97
1/2-percent values for winter from Appendix D of the International Plumbing Code. Deviations from the Appendix D temperatures shall be permitted to reflect local climates or local weather experience as determined by the building official.

Note that the Winter Design Temperature of 32 degrees, what I refer to as 'the freeze line' roughly runs along Interstate 10 across North Florida, through Texas, then up into California (where I-10 is considerably south of 'the freeze line' based on Appendix D).

Note that the building official can make it so it does not freeze where you are ... wait, let me rephrase that ... ... the building official can make it so your area ignores the freeze line as established in Appendix D, but Mother Nature can, and will, make it freeze wherever she dang well wants to - and the building official has no say in that matter.

9. ## Re: Space between insulation and sub floor

Originally Posted by chris mcintyre

I'm assuming this is regional and not code. This is the case with every crawlspace here........I can think of no exceptions.
Chris McIntyre,

Note Mathew said this was a vented (i.e. unconditioned, as in not conditioned/heated) crawlspace.

IIRC Mathew's area (Utah - specifically the greater Park City area) has extensive ammendments to the code which specify specific snow loads, rain fall, design temps, etc. for specific areas as the climate is very different terrain and geographically, altitude, valley, mountain, wind side, shade side, sun side, etc. design challenging from one location to the next. We're talking serious winter and some seasonal shifts that are a bit more challenging than you experience in SC. Protecting pipes from freezing - that's in the code. Can't put no dang heat cable/heat tape on pex - or warm it with a torch.

10. ## Re: Space between insulation and sub floor

Originally Posted by H.G. Watson, Sr.
Chris McIntyre,

Note Mathew said this was a vented (i.e. unconditioned, as in not conditioned/heated) crawlspace.

IIRC Mathew's area (Utah - specifically the greater Park City area) has extensive ammendments to the code which specify specific snow loads, rain fall, design temps, etc. for specific areas as the climate is very different terrain and geographically, altitude, valley, mountain, wind side, shade side, sun side, etc. design challenging from one location to the next. We're talking serious winter and some seasonal shifts that are a bit more challenging than you experience in SC. Protecting pipes from freezing - that's in the code. Can't put no dang heat cable/heat tape on pex - or warm it with a torch.
This is the reason I assumed it was regional, and yes, I know what happens when you assume.

Thanks for the code cite Jerry.

11. ## Re: Space between insulation and sub floor

Originally Posted by H.G. Watson, Sr.
Finally I see smaller ga. Romex stapled up on the underside (flange) of the PRIs in a crawl space - Not allowed. Only one set larger ga. allowed otherwise must be up within (See exposed work) and protected. If that's NM-B not NMC-B also NG in unfinished, unconditioned crawl.
You know why they did that, right? That was the only way they could think of to get past the RSJ. I wonder if that might be the case with the PEX as well.

12. ## Re: Space between insulation and sub floor

actually engineered truss {tji as i know it} have knockouts for such applications ,,its the engineered beams {P lam} your not supposed to compromise,,drill,notch ect,,, I personally dont thinks its that big a deal to staple romex to underside of joist,,its stapled to the top side in attics all the time,,,

13. ## Re: Space between insulation and sub floor

Originally Posted by bill hambone
actually engineered truss {tji as i know it} have knockouts for such applications ,,its the engineered beams {P lam} your not supposed to compromise,,drill,notch ect,,, I personally dont thinks its that big a deal to staple romex to underside of joist,,its stapled to the top side in attics all the time,,,
Look back at the photo... that's an RSJ those TJI's head into (also note the lack of squash blocks at the hangers). The Romex is run alongside the TJI and then descends to pass under the RSJ and then back up alongside the TJI. The same is true of the PEX, although at the tee they are running underneath and perpendicular to the joists. I suspect if the tees could have been tucked up higher they might have been able (note I didn't say inclined to - could just be the result of laziness) to run through the knockouts.

And you can drill an engineered beam (e.g. PSL/LVL) as long as you do it to manufacturer's instructions and within the engineered design limitations. For example, for a 9-1/4" iLevel LVL beam you're allowed up to a 2" round hole within the middle third of the span, with multiple holes spaced a minimum of 2x the diameter of the largest hole. I've always used a forstner bit to make clean and accurately sized/placed holes when doing so.

14. ## Re: Space between insulation and sub floor

hey Corn whats an rsj ,,it looks like a steel beam with a tji sitting on the lip of the i beam,,
thanks for the info on the drilling of p lams and such.i agree with you on the lazy part ,,

15. ## Re: Space between insulation and sub floor

Park City design temp is below zero. That PEX WILL freeze.

There was a one week period a couple of years ago working on a project up there that the temperature did not get above -6° the entire day. Yes that is a MINUS 6 degrees F!

16. ## Re: Space between insulation and sub floor

Originally Posted by bill hambone
hey Corn whats an rsj ,,it looks like a steel beam with a tji sitting on the lip of the i beam,,
thanks for the info on the drilling of p lams and such.i agree with you on the lazy part ,,
RSJ - Rolled steel joist

The TJI usually doesn't sit on the lip of the beam because the RSJ web is usually shorter than the TJI web. Sometimes see a plank (1x or 2x) on the top flange of the RSJ to make up the height difference. There is sometimes (and it looks like it in this case) solid sawn stock that is placed in the recess of the RSJ and anchored with screws through pre-drilled holes in the flanges. The joists are attached to this stock with toenails (incorrect method) or with web stiffeners (if required) and TJI hangers (correct method). As always, consult the manufacturer installation instructions for correct details. iLevel have fairly comprehensive details in their instruction sheets.

17. ## Re: Space between insulation and sub floor

i still dont know what an rsj is but if its a steel I beam,,which it looks like in the pic,,then more then likely there is a 2x or what looks like another tji ,,,with a web filler i presume ,,that sits on the beam lip that is attached with carriage bolts that hold the hangers that carries the joist,,so when its all said and done the load is on the I beam lip,,hence the joist on the lip,,not letterally but i didnt think i would need to be so specific,,

18. ## Re: Space between insulation and sub floor

Originally Posted by bill hambone
i still dont know what an rsj is but if its a steel I beam,,which it looks like in the pic,,then more then likely there is a 2x or what looks like another tji ,,,with a web filler i presume ,,that sits on the beam lip that is attached with carriage bolts that hold the hangers that carries the joist,,so when its all said and done the load is on the I beam lip,,hence the joist on the lip,,not letterally but i didnt think i would need to be so specific,,
RSJ is a specific type of I-beam - the type that is used in most residential construction.

Well, where it literally sits determines whether it needs web stiffeners or not at the end of the joist. And by "lip" I presume you bean the bottom flange. Pardon me if I can't determine from when you're being literal and when you're not being literal - I'm not that good at reading tone and intent in the words people type.

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