Thread: Wall temperature

Todays inspection has a home with a wall that was warm to the touch when the heat was operated and cool to the touch when the a/c was operated.
I noticed this when I put my hand against the wall of a closet to turn on the switch.

A return air vent is on the north part of the wall, three to four feet away, and the east part of the wall, front and back, would change in temperature. My thought was there was a supply line in the wall but above this wall was a bedroom with a vent at least ten feet back so nothing was in this section of the wall. I told my client there was no way to determine the source of the temperature change without taking a part of the wall out to see what was inside.

I'm thinking the return air vent could be damaged and pushing air in this section of the wall. What do you folks think could be the cause.
Remember, other than the return vent there is no other ductwork in this section of the wall.

You can see from these photos the temperature of the wall was 85deg with the heat on and 63 with the A/C on.

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It because your hands are warm and you did not have your bikers gloves on so it showed how warm you are

I would agree on the return air vent leaking.

Makes you wonder how the air is getting past the studs...if there were any at that area?

Originally Posted by Mike Huppi

It because your hands are warm and you did not have your bikers gloves on so it showed how warm you are

I wear those so I don't cut my knuckles on the agents teeth.

The 'return' air would not change like that. The 'return' air is the same basic temperature as that in the rooms, and it does not change that much that quickly.

The 'supply', on the other hand, DOES change that much that quickly.

I'm guessing there is a supply in there which is either leaking (a lot!) or the stud space is being used for supply air - which is not allowed.

Originally Posted by Vince Santos

I wear those so I don't cut my knuckles on the agents teeth.

I could not resist sorry sometimes I cant help myself

Originally Posted by Jerry Peck

The 'return' air would not change like that. The 'return' air is the same basic temperature as that in the rooms, and it does not change that much that quickly.

The 'supply', on the other hand, DOES change that much that quickly.

I'm guessing there is a supply in there which is either leaking (a lot!) or the stud space is being used for supply air - which is not allowed.

Like I said, there was no supply directly above that wall. There was a room above but the supply was ten feet away on the opposite wall. I was almost sure that had to be the case too but there is just no vent directly above that. Perhaps there is a vent behind that wall that just terminates in the wall and never made it to the second floor. Now that I think of that I should have went back down to the basement and checked that area for a supply.

Are you *sure* that just because the closest vent was 10 feet away that the supply could not have been run through that stud space?

To me, it makes sense (if you are going to do it wrong, who cares if you are not allowed to do it) to run up through the wall using the stud cavity, attach a transition to it, run over to the supply.

Not sure why you think that supply being 10 feet away makes it unlikely that would be the case.

Nothing else (return air would not, for sure) would make that temperature change when switched from heat to a/c.

Heck, *it could* even have a metal duct in that stud space and not even be 'wrong' in that they stud space was used, 'it may not' have been used as a supply, just used for a tight fitting supply duct, which would heat up or cool down with the heat or cooling, and change the temperature of the wall.

So 'it might not' "be wrong" in that sense. Although, a supply duct *is supposed to be* insulated, so that kinda shoots that theory down - probably not a duct in there after all.

Is this a 2 story home by chance?

Where there any refrigerant lines possibly passing down the wall void?

I've seen this before but it was at a garage wall. The wall was cold and hot as you mentioned. Come to find out, the refrigerant line in the wall was missing insulation.

How would you get different temperature changes in the same spot when you go from hot to cold from refregerent lines?

Originally Posted by Rick Hurst

Is this a 2 story home by chance?

Where there any refrigerant lines possibly passing down the wall void?

I've seen this before but it was at a garage wall. The wall was cold and hot as you mentioned. Come to find out, the refrigerant line in the wall was missing insulation.

Two story yes but no refrigerant line was installed in that area of the home. The temperature was not just always cold but hot when the heat was on and cold when the A/C was on.

Jerry, so you think that wall may have a supply line going up the wall and across the floor of the bedroom to the vent? I don't know, that would just not make and sense to me as they could have just put the vent on the floor directly above that wall instead of ten feet away.

I suppose the only way of knowing would be to apply the hammer to the wall and have a look inside.

Maybe Jerry still has that FLIR camera and you could borrow it.

He probably has it laying around in an old milk crate out in the corner of the garage collecting dust.

Jerry, so you think that wall may have a supply line going up the wall and across the floor of the bedroom to the vent? I don't know, that would just not make and sense to me as they could have just put the vent on the floor directly above that wall instead of ten feet away.

Not Jerry or an HVAC guy, but...

My understanding is that you generally want the floor registers across the room from the door in a bedroom so that the conditioned air has a chance to circulate before getting sucked back towards the return (often in the central hallway at the second floor). You also don't want them where the bed is likely to be placed. The usual result is that the registers are at or near the exterior walls. Now...we don't run heat ducts up exterior walls so a lot of bedrooms will have ducts transversing under the floors from a more central supply duct or plenum(s).

So, it does make sense that what you are measuring is a rectangular, metal, supply "riser" duct in the wall. I'm not sure those are "supposed" to be insulated or not but, as they are often the same depth as an interior stud wall cavity, I don't know how you would. I actually doubt there is any problem here at all.

The hole in the return duct idea doesn't make much sense. As Jerry said, there isn't the temperature variation and, as returns are under negative pressure, they might suck air from the framing but they wouldn't "push" air into a wall cavity.

Jerry is probably correct. It is a supply air run that is ran up then across the floor to the outside wall area for a supply area. Most HVAC installers prefer to use inside walls to run up to the second floor, as there will be less heat loss/gain if ran up an outside wall. And that run should always be insulated to keep as much desired temperature as possible.
Supply air registers are proper when installed on an outside wall with return runs on the inside walls. The supply air will put up a blanket of air to stop the penetration of outside air and then be pulled into the room by the return air runs. Hope this helps.

Thanks for the information.

Is there any way you could hook up a piece of 1/8" tubing to a manometer to check the pressure on that wall cavity?

If it is going positive with the blower running it would safe to say you have one huge supply leak affecting that space.

Might be able to make use of a smoke puffer here as well.

Originally Posted by DavidR

Is there any way you could hook up a piece of 1/8" tubing to a manometer to check the pressure on that wall cavity?

If it is going positive with the blower running it would safe to say you have one huge supply leak affecting that space.

Might be able to make use of a smoke puffer here as well.

Or that the stud cavity *is* being used as a supply duct (and it should not be).

I had, and used, a manometer, but not many HIs carry them as it is beyond the scope of what HIs do.

That's where the HVAC tech comes in, pulls out their manometer, destructively makes a hole (HIs do not 'intentionally' do destructive testing) and measure the pressure in the stud cavity. That's *their job*, the HI just finds 'What to heck???? ... Sumptin's not right here.' and the HVAC tech figures out what the problem is.

Lol.....No destruction needed for that test most returns that are using wall cavities as ducts leak like mad around the bottom plate.

Makes it nice & easy to slip that 1/8" tubing under the trim in many cases.


I am going to have to get accustomed to what the scope of work you guys really do is, still don't have as firm a grasp on that as I thought.

Learning lots of good stuff each day here.

David,

If we (HIs) started poking holes in some else's house (remember, the buyer hired us, not the owner), with some (most?) sellers, there would be major repercussions.

That's just part of our limitations.

Unlike trades, like HVAC, who are hired by the current owner to 'find and fix', we are hired by an opposing party (buyer) to the seller to 'find without touching' (so to speak).

David,
It varies from State to State, but here's a descrption of what our MINIMUM standards are supposed to be. Of course, some in our field "maximize the minimum" while others risk our butts to try to do it as we would want it done for us. I haven't figured out if the minimum guys are smarter than me or not. You should be able to link by clcking on the sections numbers in the left column.

C:\Documents and Settings\tcwalker.CIA_C5\My Documents\CIA BACKUP\TREC\SOP\Texas Administrative Code.mht

Okay, that won't work. Let me try to convert the doc and see if I can post the link. It's too long to post in the reply.

Okay, that didn't work. DUH!

The form we use as a Base report can be found here.
http://www.trec.state.tx.us/pdf/form...ctonReport.pdf

The provisions have been converted from .mht (whatever the hell that is) to pdf. I have attached. Hope it helps all of you to understand what we do in TX. I don't know what they do in the U.S.

This inspection was a warranty inspection so I told the owner I could remove some of the wall to try and determine the source. Obviously he was not so worried about the issue that he was willing to allow me the opportunity. We talked about a couple possibilities but in the end it was just educated guesses.

For reporting purposes I simply stated what I found and with the limited visual inspection I was unable to determine what the cause was.

I would like to be able to dig deeper and find out exactly what the cause is but my hands are tied. Even offering a couple possibilities as to what is causing the problem is stretching it as they are only educated guesses. Educated guesses could come back to bite the inspector if it turns out to be something different. Especially if it's a larger issue than what was discussed.

Originally Posted by Vince Santos

I would like to be able to dig deeper and find out exactly what the cause is but my hands are tied. Even offering a couple possibilities as to what is causing the problem is stretching it as they are only educated guesses. Educated guesses could come back to bite the inspector if it turns out to be something different. Especially if it's a larger issue than what was discussed.

Not if worded properly and noted that this is only one of several possibilities, and, the final outcome could be much more involved.

Basically, you are stating 'I think it could be this, or that, or anything else, so address it before closing or take the risk that it is a more involved problem than I suspect.

I did not let things like that hamper me from advising my clients of things, I did it for over 16 years. You should never be afraid of offering you professional opinion on what you think it is.

You only run into problems when you say 'THIS IS THE CAUSE ... ', and even then, if you are not hiding something, I doubt you will be put in a pinch because of saying that - you gave your professional opinion.

*I* preferred to couch my opinion in 'possibilities', as in 'this is what I think the problem could be'