Message Board Thread - "Air leakage or steel lintel conduction"

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Air leakage or steel lintel conduction Ben10 10/29/2008
I to all.
I have join some pictures of new aluminium windows in a brick wall. The wall is insulated with 75mm of polyurethane and as a air space of 30mm between insul. and brick.
Those pictures where taken at 10Pm. The ext. temp was 8degC and the int temp. was 18degC. A light ''est'' wind 7km/h put this wall facing west in positive pressure.
What do you think can cause the colder area over the windows.
Thanks for yor time.
 
Re:Air leakage or steel lintel conduction MR. EXCELLENCE 11/1/2008
I think its the aluminium windows. they just cooled off way faster they the exterior brick building. i don't think that is air leakage. you should have some kind on steel lintel system above the windows. thats why you see the cooler areas above the windows. some of the windows show the cooling out past the windows at the top. not much but just a bit. how far away were you when you shot this wall? the steel lintel above the windows will have steel rebar sticking up for the next row of brick.

The yellow line you see between the first and second story windows is some minor air exhail from the building or from the siding over the brick. you may have a moisture problem in some of the upper windows. I would want to do a water test on them.
 
Re:Air leakage or steel lintel conduction Ben10 11/3/2008
I MR. EXCELLENCE.
The prwevious picture was taken from +/- 60 Feets. This one was from +/- 20 feets away. I think you'r right. The steel lintel must cool the bricks faster than the rest of the wall around it. Those pictures were taken at night around 10 pm. Taking into account that most of the day was sunny and that the wall is facing south west, if there was humidity over the lintel, it should show warmer than the wall. Am i right. I will go check for humidity this week and let you know.

 
Re:Air leakage or steel lintel conduction Thermographer 27652 12/9/2008
MR. EXCELLENCE wrote:
its the aluminium windows. they just cooled off way faster they the exterior brick building. i don't think that is air leakage. you should have some kind on steel lintel system above the windows. thats why you see the cooler areas above the windows. some of the windows show the cooling out past the windows at the top. not much but just a bit. how far away were you when you shot this wall? the steel lintel above the windows will have steel rebar sticking up for the next row of brick.

The yellow line you see between the first and second story windows is some minor air exhail from the building or from the siding over the brick. you may have a moisture problem in some of the upper windows. I would want to do a water test on them.
The brick wall is the west elevation of the building. I assume the building is in the northern hemisphere. Thus, the temperature of the brick increased while the sun was on the brick. The glass windows did not retain any heat from the exposure to the sun. The aluminum window sash is warmer than the glass since the heat from the brick is transferring into the aluminum sash.
 
Thermographer 27652 Thermographer 27652 12/9/2008
MR. EXCELLENCE wrote:
its the aluminium windows. they just cooled off way faster they the exterior brick building. i don't think that is air leakage. you should have some kind on steel lintel system above the windows. thats why you see the cooler areas above the windows. some of the windows show the cooling out past the windows at the top. not much but just a bit. how far away were you when you shot this wall? the steel lintel above the windows will have steel rebar sticking up for the next row of brick.

The yellow line you see between the first and second story windows is some minor air exhail from the building or from the siding over the brick. you may have a moisture problem in some of the upper windows. I would want to do a water test on them.
The brick wall is the west elevation of the building. I assume the building is in the northern hemisphere. Thus, the temperature of the brick increased while the sun was on the brick. The glass windows did not retain any heat from the exposure to the sun. The aluminum window sash is warmer than the glass since the heat from the brick is transferring into the aluminum sash.
 
Re:Air leakage or steel lintel conduction GRG Ottawa 12/10/2008
You mention that the wall faces west in your posting, then later southwest. Given the outdoor air temperature and the date of your posting, and the indoor / outdoor temp. difference, the image was likely made shortly after sun set. The wall is still hot from solar gain. You should make such scans during much colder weather, and long after sun set. Because you haven't, you are forced to interpret a difficult thermal image.

Your close-up is revealing. Surfaces that "see" the cooler window glass are cooler than those that face away from the window glass. That is normal. That indicates the frames are still warm from direct solar gain and heat gain from the adjacent brick cladding.

The cool spot above the windows may be related to wind movement. You noted that the wall was under positive pressure. Wind will move up the face of a wall under positive pressure; the cool plumes above the windows may simply be chilling from air that has passed over the windows, cooling the brickwork above.

You should repeat the scan under correct conditions to get a more meaningful image of the thermal signature of this wall.
 
Re:Air leakage or steel lintel conduction Ben10 12/10/2008
GRG Ottawa wrote:
tion that the wall faces west in your posting, then later southwest. Given the outdoor air temperature and the date of your posting, and the indoor / outdoor temp. difference, the image was likely made shortly after sun set. The wall is still hot from solar gain. You should make such scans during much colder weather, and long after sun set. Because you haven't, you are forced to interpret a difficult thermal image.

Your close-up is revealing. Surfaces that "see" the cooler window glass are cooler than those that face away from the window glass. That is normal. That indicates the frames are still warm from direct solar gain and heat gain from the adjacent brick cladding.

The cool spot above the windows may be related to wind movement. You noted that the wall was under positive pressure. Wind will move up the face of a wall under positive pressure; the cool plumes above the windows may simply be chilling from air that has passed over the windows, cooling the brickwork above.

You should repeat the scan under correct conditions to get a more meaningful image of the thermal signature of this wall.
Thanks for your time GRG. I realy appreciate. I will repeat the scan under differents conditions.
 


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