Message Board Thread - "Tony"

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Tony ati 2/11/2010
I just performed thermograpgy on this dwelling and ran into a problem. There is consistent heat loss going around the whole house. The exterior temperature is 0.4 C. There is very little air movement. The front and rear of this house is showing heat loss (3-4 C) and runs from the eve to the top of the windows. The gables also show heat loss running along the roof line from the eve and below (to top of gable vent). The heat loss in the gables can be contributed to heat loss in the dwelling into the attic from many areas of the house, and banking near the roof due to inadequate air flow. The walls are another matter. What would cause such a consistent heat loss in the top portion of the walls (front and back)? Client just bought this house and believes there is batt in the wall and that the soffits are not blocked. My first guess was settled blown-in insulation for the walls and inadaquate air flow for the gables.
Re:Tony Top Gun 2/11/2010
How much of an overhang is there from the wall to the edge of the roof? I assume that it is at least a foot, and that the sky is clear. Under these assumptions, radiant heat loss from the surface of the vertical wall will be maximized in the central and lower part of the wall since that area is most exposed to the COLD sky. As you look closer and closer to the top of the wall, from the perspective of a point on the wall, along this area, more and more of the sky is covered by the overhang, reducing the radiation to the sky. At the same time, higher areas of the wall have a better view of the ground which is much warmer than the COLD sky. It is like the "corner effect" but in reverse since the viewer is outside. Remember what the camera sees is the "process" of energy moving from warm to cold, and the dynamics are ever adaptive. You may see a different effect if the sky was overcast with low level clouds that are similar temperature as the surface air and perhaps the ground. You should have looked at a nearby house with no overhang and checked for this kind of thermal characteristics there as well. That's my opinion.
Re:Tony Top Gun 2/11/2010
Oh, and look under the stairs and what looks like an elevated deck. It is warmer under there as well. Radiant heat loss is at least 50 percent to 70 percent more efficient than "natural" convective heat loss. Interesting scenario.
Re:Tony ati 2/14/2010
Interesting explanation of what is happening here. I went back during the daytime, it was overcast, exterior temperature was higher and rat was significantly lower (-22 for clear night and +4 for daytime). The house imagery came out to what I have being doing for this style and age of house. The heat signatures at the eves around house and under the steps have disappeared. There is a little exposed heat loss at the base (foundation), more significant at the front overhang, a little elevated above the windows, and in the attic area. It appears your explanation may be correct given no other explanation. Checking other nearby houses is certainly a good idea for future reference.
Re:Tony happlin 3/3/2010
This looks like the lower r-value of headers and top plates. You see the same problem at the bottom of the wall from the sill plate and band joists. Interesting that the wall studs are visible. It is possible that there is a sagging of insulation that is pulling insulation from the top of the wall.
Re:Tony TexasHomeInspector 3/6/2010
Comment and a question. I’ve had my Level One certification only a few months now and this picture looks pretty common for what I’ve seen. From my very limited IR experience, it looks like that the rising heat in the house collects in the ceiling due to the insulation resistance and has a spilling effect at the eves. Look closely at the eaves above the windows and the eaves appear warmer probably due to the window reflections. Looking at the roof surface, from what I see there doesn’t appear to be much heat buildup.
I was wondering if you could explain the heat at the foundation/soil surface. I assume it’s due to heat buildup in the concrete and conducts at the soil contact.
Re:Tony ati 3/13/2010
I believe that there are multiple interactive answers to this image. Top Gun is correct for the front of the house but not for the whole house. As I stated above the conditions disappeared when I went back under different daytime conditions. The condition in the front at the eves was exactly the same around the other 3 sides of the house where there is no overhang near the base. The condition at the front step was not repeated at the rear deck. I believe that due to the cold sky and warm ground (the ground around the house was bare for about 6 feet and the rest was snow covered) helped in the exaggerated conditions (heat signatures) occurring. Heat from the ground could have been a contributing factor. There was also very little air movement. The heat signatures under the front step were a result of heat loss from the overhang and probably the foundation and ground helping. It probably contributed to the heat signature at the eve at the front as well (temperature was a little higher at the front than the other three sides). There was also significant heat loss from the dwelling into the attic. This heat created a uniform heat signature around the dwelling at the eves (remember there was very little air movement that night). I believe this is a combination of factors that led to these images. There is probably even more here that what everyone has come up with so far. Either way, good discussion.


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