Coming Soon to NJ - 12.35 kW Hanwha DUO-G5 + SolarEdge Inverter/Optimizers by GPE

[sunpoweredev]

NJturtlePower any updates on your install? I received PTO yesterday

[macaddict]

Finally got a chance to go in the attic and take some pictures.

This first picture shows the temperature on the side of the roof facing the attic (inside).

The right side is the north facing side of the roof. The left side is the south facing side of the roof and is where the solar panels are installed.

The red hot (almost white) area to the right of the blue is the space between the solar panel and the peak of the roof on the south side. This is reading 141.8 degrees F:
20190726T162628.jpg

The area under the solar panels is blue and showing 117.8 degrees F

20190726T162638.JPG

Here is another shot of the south side of the roof showing an area where solar panels are installed (blueish) and an area where they are not (reddish). This is the area of the roof where the attic vent is (from my previous post).

20190726T162726.JPG

All of these pictures are from the upper roof area. I would've had to crawl across the attic to get to the lower roof area which I didn't want to do

[J.P.M.]

You are correct that there are 2 roof areas. The lower (with the chimney) doesn't have panels.

I'm assuming that the temperature between the panel and the roof is similar to what is on top of the panels. I could go in the attic and take a picture from there...

Measurements I've done at min. daily array solar incidence angle max. with an infrared thermometer (not a camera) of exposed roof deck, roof deck under the array, and panel back surface temperatures generally have exposed roof deck at amb. temp. + ~ 40 C., roof deck under array at ~ amb. temp. + ~ 10 -15 C, and back panel temp. at ~ amb. + ~ 30 C. All those readings are variable as f(P.O.A. incidence, wind vector) but were all under clear skies and under full sun at various times of the year, but always under clear skies and at daily time of min. solar incidence angle on the array. Less P.O.A. irradiance such as in the winter at lower solar incidence angles and all the temp. differences are lower.

Infrared cameras with wide fields of view taking in many objects with different emittances in the infrared cannot account for different materials emissivity in the infrared frequencies. Glass, being highly reflective to infrared radiation, will show differently than, say, roof shingles which have pretty much constant reflective and absorbance across the electromagnetic spectrum.

Flir has a good blurb explaining +'s and -'s and limitations of thermal imaging.

FWIW, bottom line from work I've done: Temps. from higher to lower under full sun: Exposed roof deck, panel front glazing, panel back surface, roof deck under the array.

After that, it can and usually does get complicated rather quickly.

[nwdiver]

I'm surprised that the panels are so much cooler than the roof surface.

Unless you're looking at a surface like glass straight on with IR you're likely reading the thermal image of what's being reflected... in this case the sky. Glass is a pretty good mirror for IR.

[JSchnee21]

I'm surprised that the panels are so much cooler than the roof surface. I would expect the panels to be darker and absorb more heat. But, I guess the air space underneath from the racking keeps them cooler than the roof? Presumably the white back sheets help as well.

Presumably, then, if the panels themselves are cooler, then the roofing under the panels would be cooler still. Save for conducted heating from exposed roofing, convective heating from within the attic itself, and radiant heat from the backs of the panels.

[macaddict]

At first I thought this was before and after, then I realized it's just a different angle.

Upper roof has panels and lower roof none, but aren't you really just reading the panel temp? Thermal picture of the inside of the attic spaces would be more definitive no?

You are correct that there are 2 roof areas. The lower (with the chimney) doesn't have panels.

I'm assuming that the temperature between the panel and the roof is similar to what is on top of the panels. I could go in the attic and take a picture from there...

[NJturtlePower]

Another benefit of solar panels is that they lower the temperature of your roof. In these pics you can see the different of the roof temperature where I have solar panels and the spots where I don't.
20190721T113846.JPG20190721T113855.JPG

At first I thought this was before and after, then I realized it's just a different angle.

Upper roof has panels and lower roof none, but aren't you really just reading the panel temp? Thermal picture of the inside of the attic spaces would be more definitive no?

[macaddict]

Another benefit of solar panels is that they lower the temperature of your roof. In these pics you can see the different of the roof temperature where I have solar panels and the spots where I don't.
20190721T113846.JPG20190721T113855.JPG

[macaddict]

Just thought of something here. Perhaps 6-8 years ago, there were two houses here within the next two blocks had a complete teardown of the old roof and new one put on. At the time these houses were only about 5-7 years old, and I've always wondered why. No they don't have a solar system on the roof. Both of these houses are owned by "more mature" couples.

Knowing how inefficient this house was (probably still is), I do wonder if I get the attic re-insulated if it'll further improve things, knowing that the insulation up there right now is probably crap. To you guys who have re-insulated your attic, what was the cost so that I'll have a rough idea and decide whether to look into it?

OP, I'm sorry I keep clogging up your thread.

My house is ~ 30 years old. I had an energy audit done this spring through the NJ Clean Energy program. I think I paid $300 for the audit and if I had gone forward with the same company for the insulation work, they would've credited it to me. The NJ Clean Energy program also had rebates/low interest loans to help.

I ended up going with North Pole Insulation. I had the rim joists spray foamed in the basement ($1,000) and had an additional layer of R30 fiber glass insulation in the attic on top of the 6" that the builder put on ($1,640). I'm not sure the square footage of the attic but the house is 3,800 sq ft. These prices were less than half of what the energy audit company wanted (even after the NJ Clean Energy rebates). It would've been cheaper if I had gone with blown in insulation but I had that on my last house and hated it, it got in everywhere and if I ever needed to go to the attic, it was a hassle.

I can certainly feel the difference. In the basement, my dehumidifier actually cycles on and off which it never did. On the second floor, it is much cooler (only have a 1 zone hvac system). I also have a FLIR thermal camera and I no longer see hot spots when pointing it to the ceiling on the second floor. Definitely a good investment.

[sunpoweredev]

Just thought of something here. Perhaps 6-8 years ago, there were two houses here within the next two blocks had a complete teardown of the old roof and new one put on. At the time these houses were only about 5-7 years old, and I've always wondered why. No they don't have a solar system on the roof. Both of these houses are owned by "more mature" couples.

Knowing how inefficient this house was (probably still is), I do wonder if I get the attic re-insulated if it'll further improve things, knowing that the insulation up there right now is probably crap. To you guys who have re-insulated your attic, what was the cost so that I'll have a rough idea and decide whether to look into it?

OP, I'm sorry I keep clogging up your thread.

[J.P.M.]

If installing ridge vents was per code, then the builder here ignored it. I didn't even know about ridge vents until I saw the quote on the new roof. The standard roof venting in this subdivision here is 2 or 3 (depending on the model on the house) of those square vents, and a single powered attic fan was a $400 option. I guess they pray on the ignorant, although this builder was extremely rigid on options, so even had I known about proper attic venting and requested it they would've told me to get lost. If it was not on their menu, it positively cannot be done no matter what you offer to pay. I wanted one extra soap dispenser by the kitchen sink and different wall paint colors. Nope can't do it. This was not our first house, but let's admit it, the average younger home buyer will not bother to learn about attic venting. Live and learn.

The attic fan's thermostat was set to 120 degrees. In weather like this week's, the fan would be on all day long and the upstairs AC (set to 82 during the day) will run pretty much non stop by early afternoon and it will not be able to keep up, rising to like 85 upstairs. With the new roof, the upstairs AC finally kicked on around 5pm when it was 92 degrees out.

lux1.JPGlux2.JPGlux3.JPG

among other things, the vent system, including vents and fans may be undersized and/or conditions may be beyond the design conditions.

[sunpoweredev]

Strange, I was under the impression that ridge vents were part of standard building code requirements for the past 15-20 years. I've not seen new construction in quite a while that didn't have ridge vents.

That said, I'm of the impression they don't really work as well as they're intended. My house also has full soffit vents all around (perforated vinyl siding) and when we had the attic re-insulated we were careful to have baffles installed to keep the insulation from blocking the holes. When we re-roofed as part of having solar installed, it seemed like a given that ridge vents were the standard thing (they replaced ours with a new one). I asked about having it removed, but they said it was required.

That said, I've never felt like the ridge vent does very much. I'm sure there is some convection, but the attic still get really hot >120F in the summer. Powered attic fans are nice, usually you need multiple as their CFM is pretty low (compared to the volume of the attic) and of course you need sufficient inlet venting to accommodate the outgoing CFM. In my case I had one installed when I got new sky lights. But, it's right up by the ridge vent (within 2 or 3 feet) so it's probably just wasting energy recirculating fresh air from outside.

You'd do better to have two or more powered gable vents either blowing across the space (one in, one out) or both in if you have a ridge vent to exhaust. If you get really fancy, they have foil lines OSB as well which is excellent for keeping the suns heat out of your attic (though they do have a few challenges). They also have solar shingles with high IR reflectance -- though these are 30-40% more expensive.

If installing ridge vents was per code, then the builder here ignored it. I didn't even know about ridge vents until I saw the quote on the new roof. The standard roof venting in this subdivision here is 2 or 3 (depending on the model on the house) of those square vents, and a single powered attic fan was a $400 option. I guess they pray on the ignorant, although this builder was extremely rigid on options, so even had I known about proper attic venting and requested it they would've told me to get lost. If it was not on their menu, it positively cannot be done no matter what you offer to pay. I wanted one extra soap dispenser by the kitchen sink and different wall paint colors. Nope can't do it. This was not our first house, but let's admit it, the average younger home buyer will not bother to learn about attic venting. Live and learn.

The attic fan's thermostat was set to 120 degrees. In weather like this week's, the fan would be on all day long and the upstairs AC (set to 82 during the day) will run pretty much non stop by early afternoon and it will not be able to keep up, rising to like 85 upstairs. With the new roof, the upstairs AC finally kicked on around 5pm when it was 92 degrees out.

lux1.JPGlux2.JPGlux3.JPG

[J.P.M.]

The other problem is that most ceilings are quite leaky...holes for light boxes, recessed lights, bathroom fans, HVAC registers/improperly sealed ducts are all places for significant loss of conditioned air once the fan depressurizes the attic.

Agreed. But agreeing is not the same as saying sloppy reality is acceptable. I retrofitted my first home built in 1928 and got the air change rate below 0.5 air changes/hr. Interesting blower door techniques that were slightly off std. when done in the late '70's.

Besides, with adequate vent inlets for the attic, the delta P is quite small - a couple of velocity heads maybe.

[malba2366]

That's why about half of the ventilation exercise involves inlet sizing considerations. Unfortunately, that's usually the part that's not considered.

An attic fan can do a lot of good. It's the crappy design process for the entire poor execution of the application that usually causes the problems.

The other problem is that most ceilings are quite leaky...holes for light boxes, recessed lights, bathroom fans, HVAC registers/improperly sealed ducts are all places for significant loss of conditioned air once the fan depressurizes the attic.

[JSchnee21]

Strange, I was under the impression that ridge vents were part of standard building code requirements for the past 15-20 years. I've not seen new construction in quite a while that didn't have ridge vents.

That said, I'm of the impression they don't really work as well as they're intended. My house also has full soffit vents all around (perforated vinyl siding) and when we had the attic re-insulated we were careful to have baffles installed to keep the insulation from blocking the holes. When we re-roofed as part of having solar installed, it seemed like a given that ridge vents were the standard thing (they replaced ours with a new one). I asked about having it removed, but they said it was required.

That said, I've never felt like the ridge vent does very much. I'm sure there is some convection, but the attic still get really hot >120F in the summer. Powered attic fans are nice, usually you need multiple as their CFM is pretty low (compared to the volume of the attic) and of course you need sufficient inlet venting to accommodate the outgoing CFM. In my case I had one installed when I got new sky lights. But, it's right up by the ridge vent (within 2 or 3 feet) so it's probably just wasting energy recirculating fresh air from outside.

You'd do better to have two or more powered gable vents either blowing across the space (one in, one out) or both in if you have a ridge vent to exhaust. If you get really fancy, they have foil lines OSB as well which is excellent for keeping the suns heat out of your attic (though they do have a few challenges). They also have solar shingles with high IR reflectance -- though these are 30-40% more expensive.