Why is my house so hot?

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Originally Posted By: 28oz
Originally Posted By: ARCOgraphite
You ABSOLUTELY need gable end vents with forced expulsion on one gable. That be a thermostat controlled fan Hopefully you have UNBLOCKED soffit vents also.


I'm looking at putting in a thermostat controlled fan in one (or more) of my gable vents. I've blown in more insulation and added some reflective barriers.....both of which have helped.....but, I think more can be done. I'm curious, does it matter which gable vent you use (I have them on every side of the house except the south facing)? If it matters, how do you determine the best gable vent to put one in?


Spend some time studying the topic on the interweb. It's been a few years since I did, but if you are not very careful you can create problems with powered gable fans. If memory serves, I think the gist of the problem is that an exhaust fan can create negative pressure in the attic. This can disrupt natural venting (ridge/soffit) AND it can "suck" conditioned air out of the living space through any unsealed cracks. This in turn can create negative pressure in the living space and draw in hot moist air from outside. Not good.

A few articles I found in a few seconds: https://www.energyvanguard.com/blog/75600/The-1-Reason-Power-Attic-Ventilators-Don-t-Help
http://www.greenbuildingadvisor.com/blogs/dept/musings/fans-attic-do-they-help-or-do-they-hurt

Cujet's advice about radiant heat is spot on also. Managing attic heat is much different in the south vs the northern climates.
 
Originally Posted By: Fitter30
Have looked at your swamp coolers. Have the pads been replaced, water level, pump, blower wheels clean, did they ever work. If they take all their air from outsider any windows open to relieve the air.
i have double padded them and added bigger pumps. They work well as long as they are on and its less than 100 outside. Once over 100 or them off for the night the house heats up in a matter of seconds.
 
Why would you turn them off for the night?

The way to go with coolers is the Master Coolers with the 6" thick pads. Those straw pad coolers are garbage.
 
Originally Posted By: Cujet
The simple answer is to have a white roof. Here in South Florida, we've learned that radiant heat from a dark roof permeates the house. It matters very little if the attic is vented. The heat is radiant, and comes right through fiberglass insulation and drywall.

EDIT: Guess what color my roof is? White, barrel tile. I have a very efficient Florida house and my utility bills are very reasonable. The builder thought I was crazy when I declined the expensive attic insulation package, and instead went for insulated low-e windows. Unlike my old home, I can't feel any radiant heat from above.
Very good points. White barrel tile is great. Far too many new McMansions here with complicated roofs sheathed in black/dark asphalt or same color in metal. You can't thumb your nose at Mother Nature without steep, thermal consequences.

My new shingles are white/silver with tiny dots of green for color. They also contain copper which prevents mold & mildew from taking root. On the opposite side of the ply decking is a sprayed-on radiant barrier. A continuous ridge vent runs from one end to the other. Soffit vents below have more sqr. in in area than ridge vent does (which is critical). Attic floor insulation is about R-35 fiberglass batts.

I don't feel attic heat on my face at all. I've noticed this odd effect though at other houses (even with 10' & 12' ceilings) as our face is quite good at detecting heat sources.

Despite my air-cond being off for several days now, it's currently 88F and 55% humidity inside. Warm but doable with a fan blowing in my face as I type. With air-cond working, it would usually be 78F and 35% Rh given how dry it currently is outdoors.

Outdoors:
Ambient T: 100F
Rh: 46%
Wind: 0 mph
Heat Index: 115F
Solar Intensity: 952 W/m^2.
Solar Heat Index: 134F

Finally, here's another odd sight I noticed in someone elses home: We were sitting around a dining table in a medium sized room facing West. The sun was on the glass with fabric shades indoors. You could feel the heat. I could also feel it on my face from the ceiling. The A/C finally clicked on and the sun rays were just at the right angle to illuminate the dust suspended in the air. Once the cooler air began rushing out of the ceiling vents, I could see all of these "sparkly" particles go by....almost like micro-scopic 'glitter'. I guessed they had a leaky duct-system: As the air rushed down the duct, it pulled in attic fiberglass & dust through the leak(s) due to the Venturi Effect, "showering" the occupants. Of course, it was also pulling in hot, dirty attic air.

This would explain the suspended particles when the A/C was off. This is also why fancy expensive A/C filters are a waste of money if your duct system has leaks.
 
Originally Posted By: Chris142
Originally Posted By: Fitter30
Have looked at your swamp coolers. Have the pads been replaced, water level, pump, blower wheels clean, did they ever work. If they take all their air from outsider any windows open to relieve the air.
i have double padded them and added bigger pumps. They work well as long as they are on and its less than 100 outside. Once over 100 or them off for the night the house heats up in a matter of seconds.
Have you hosed down your roof and all of the asbestos siding?
 
As a quick experiment, I took some IR readings before and after.

Before:
Sunny roof: 137F
Shady roof: 89F

Sunny wooden South-facing siding painted a light color:115F
Shady wooden East-facing "" "" """: 91F

Sunny limestone walkway: 125F

After watering:
Sunny roof: 100F
Shady roof: 81F

Sunny wooden South-facing siding painted a light color:97F
Shady wooden East-facing "" "" """: 80F

Sunny limestone walkway: 95F
 
Even in 115 degree heat, I've never felt heat from the ceiling from any house, even touching it. I'm sitting in my grandpa's 1950 house right now and just felt the ceiling, cool as a cucumber.
 
Originally Posted By: Nick1994
Why would you turn them off for the night?

The way to go with coolers is the Master Coolers with the 6" thick pads. Those straw pad coolers are garbage.
if I leave it on at night I have to get up to turn it off when I get too cold. The cooler is a mastercool but with 4 inch thick pads. They were horrable! I tried every type and the straw was the best by far.
 
96 degrees in daytime but at night it gets too cold?
I will take too cold any day.
You can always put another blanket on.
 
Your house is hot because it absorbs more energy from sunshine than it can shed at the same time. You can minimize heat absorption and you can increase heat shedding. My concern would be the heat during the daytime rather than cold nights. You can always put on more clothes, but you can take off only so much.
Is there always a breeze blowing at the edge of the desert? Insulation and a black roof will help. Black sheds heat best. That's why bedouins and radiators are commonly clad in black.
If no breeze is blowing, your best bet is a white colored roof, because it will reflect much of the incoming radiation back.
You could even construct a Land Rover type safari roof a couple inches above your current roof. which will help keep insulate the house.
 
I had three turbines installed for years with a gray fiberglass shingle roof, it has two gable vents and 6 eve vents plus a 30" hole in the garage ceiling open in the summer.

I had a new roof put on and used dark shingles with ridge venting.

I did not work well and the temp in the attic skyrocketed. It actually caused the resin in the 60 year old wood to bead out.

I took the ridge venting out and put back three new turbines and all is now well.
 
Originally Posted By: Chris142
My house is not well insulated. I get that. It was 106 today and we had the coolers on which kept the house bearable. The sun set and its now 85 degrees outside. I turned off the cooler and now its 96 in the house! Why did the temp go up and above the outside temp? My wife thinks it's built on lava.


If you are cooling your house with evaporative cooling, (swamp coolers), look into up duct discharge. Instead of running with the windows open. Most any heating and cooling company out in the desert can install these. I had them when we lived in Lake Havasu City with my Master Cool Evap cooler.

They are mounted by cutting a hole in the drywall of your ceiling. They work by having a spring loaded flap that opens when you run your evaporative cooling. As soon as you turn on the cooler, (with the windows closed), it pressurizes the house, and the up ducts automatically open, exhausting the cool interior air into the attic, and out the attic vents. The contractor will determine if you have enough area in you attic vents. If not they can install a couple of turbine vents.

This will be far cheaper than putting in powered attic fans. And it will work much better. When I had them, and my evap cooler was running after an hour or so, my attic was as cool as the interior of the house. I could actually stand outside and feel the cooler air sinking off the roof, out of the attic vents on a calm day. It made an unbelievable improvement.

Lowe's even sells them if you want to install them yourself. They are very easy to install. With a cordless drill and a jig saw you can have one installed in about 10 minutes. I believe they even come with a template to guide you on how big of a hole to cut, and where to drill.

https://www.lowes.com/pd/Dial-Galvanized-Steel-Plastic-Grille-Evaportative-Cooler/3094543
 
Originally Posted By: doitmyself
Originally Posted By: 28oz
Originally Posted By: ARCOgraphite
You ABSOLUTELY need gable end vents with forced expulsion on one gable. That be a thermostat controlled fan Hopefully you have UNBLOCKED soffit vents also.


I'm looking at putting in a thermostat controlled fan in one (or more) of my gable vents. I've blown in more insulation and added some reflective barriers.....both of which have helped.....but, I think more can be done. I'm curious, does it matter which gable vent you use (I have them on every side of the house except the south facing)? If it matters, how do you determine the best gable vent to put one in?


Spend some time studying the topic on the interweb. It's been a few years since I did, but if you are not very careful you can create problems with powered gable fans. If memory serves, I think the gist of the problem is that an exhaust fan can create negative pressure in the attic. This can disrupt natural venting (ridge/soffit) AND it can "suck" conditioned air out of the living space through any unsealed cracks. This in turn can create negative pressure in the living space and draw in hot moist air from outside. Not good.

A few articles I found in a few seconds: https://www.energyvanguard.com/blog/75600/The-1-Reason-Power-Attic-Ventilators-Don-t-Help
http://www.greenbuildingadvisor.com/blogs/dept/musings/fans-attic-do-they-help-or-do-they-hurt

Cujet's advice about radiant heat is spot on also. Managing attic heat is much different in the south vs the northern climates.


Thanks for the input. I've read that also about creating a negative pressure not being a good thing. Right now, I'm just keeping an eye on my attic temps.
 
I would exhaust out the north end so there is less chance of fighting a natural wind. But the fan and gable have to be sealed for the fan to be effective. And if you are sucking up air from the inside that needs to be sealed off. Better to exhaust out the roof in the center IMHO.

The underside of the roof should be the same temp as the top side.
 
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