# 1971 Mansard Attic Ventilation Nonexistent



## seeyou (Dec 12, 2008)

How well is the attic insulated?

I'm guessing that the area between the steep slope of the roof and the interior wall is probably not connected to the lower pitch attic area. 

Some at this forum are advocates of edge venting. I've never used it, but it might be an option for the upper roof edge. 

Another option would be to add some type of dormer vents.


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## 1971Mansard (Jun 15, 2010)

Yes th events at the bottom of the roofline, which were meant to vent into the attic were blocked at some point at the slope change on the roofline. 

I have about 6" of insulation in floor of the attic.


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## seeyou (Dec 12, 2008)

1971Mansard said:


> Yes th events at the bottom of the roofline, which were meant to vent into the attic were blocked at some point at the slope change on the roofline.
> 
> I have about 6" of insulation in floor of the attic.


I'd pursue adding more insulation, ie, blow in cellulose (at least 6") over the existing. You don't say where you're located, but you must be at least kind of south with that cooling problem. 

Are the exhaust vents on the rear plane(s)? Maybe add some more down lower for inlet. By adding insulation, you reduce the need to get the heat out of the attic. You also reap the benefit of less heat loss in winter. It does need some venting to remove any moisture that escapes from the living space. 

Got pull down attic stairs? How well are they sealed?


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## 1971Mansard (Jun 15, 2010)

I just got off the phone with a roofing subcontracting. He did not believe that adding inlets would provide any improvement to the temperature inside of my house, that the only option would be to add a dedicated AC unit outside for the 1st floor. 

This is contrary to what I have heard on these forums. I have had an AC crew look at by HVAC system and they said my AC output should be enough to cool my first floor. 

thoughts?


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## seeyou (Dec 12, 2008)

1971Mansard said:


> I just got off the phone with a roofing subcontracting. * He did not believe that adding inlets would provide any improvement to the temperature inside of my house,*that the only option would be to add a dedicated AC unit outside for the 1st floor.
> 
> This is contrary to what I have heard on these forums. I have had an AC crew look at by HVAC system and they said my AC output should be enough to cool my first floor.
> 
> thoughts?


I would tend to agree to a point. But the reason it's so hot upstairs is that the heat from the attic is coming through the inadequate insulation. Before I bought more AC equipment, I'd try the cheap, relatively easy fix that will benefit you year round and also benefit you even if you have to get more A/C equipment. Add some insulation.

I had a similar problem. 6" of chopped fiberglass and a 25 year old A/C unit that could barely keep the house tolerable running full blast all day long. Blew in 8-12 inches of cellulose on top of the fiberglass on a 95 degree day. It was 79-80 degrees in the house when we started. 4 hours later when we finished (about 2PM on a sunny day), it was down to 76 degrees and the A/C was cutting off occasionally. 

If there ever was a DIY project, blowing cellulose in an attic like yours is it. I'd remove a few shingles in several places and cut some holes in the sheathing and blow from outside. Patch the hole back in, replace the shingles and move to the next spot. Or hire it out. 

If the added insulation doesn't get it cool enough, pursue the second A/C unit. I bet you don't have to. 

Have the HVAC guys looked at the air returns? The system may be unbalanced.


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## 1971Mansard (Jun 15, 2010)

No, I dont have any pull down stairs, unfortunately. 

I will definitely be blowing more insulation, any idea on how much that costs (1400 sq. ft.)?

I do still want to add inlet vents at the eaves though.


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## JakAHearts (Apr 20, 2010)

I cant help too much with the question but your house is beautiful.

Shane


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## seeyou (Dec 12, 2008)

1971Mansard said:


> No, I dont have any pull down stairs, unfortunately.
> 
> *I will definitely be blowing more insulation, any idea on how much that costs (1400 sq. ft.)?*
> 
> I do still want to add inlet vents at the eaves though.


A bale (16 cu ft) runs about $9 locally. 40 bales would give you 6"-8"+ of additional insulation (10" of cellulose is R38, IIRC). The big boxes will "lend" a blower if you buy the bales from them. So, it looks like about $360. Probably a little over twice that to hire it out.



JakAHearts said:


> I cant help too much with the question but your house is beautiful.
> 
> Shane


That is a nice looking house.


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## Yoyizit (Jul 11, 2008)

There are many reports on the Web about attic ventilation and it depends on several variables. Some reports may disagree with others for reasons known or unknown.

You could also ask each contractor what he bases his choice on.

I'd probably rent a fan, make a temporary exhaust and intake vent and determine how many air changes per hour you need to do a reasonable job of lowering your room temps, on a typical sunlit, windless day in your area. If there is no noticeable room temp. difference at high CFMs at mid afternoon you'll need some other method.

I see that you live in a place with seasonal change. To some extent your latitude will affect your results.


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## Ed the Roofer (Jan 27, 2007)

You would need to inastall a continuous exhaust vent at the top of the mansard wall and also a continuous intake vent system at the bottom of the mansard.

Before they had such a product available for the mansard wall exhaust application, I re-configured an existing piece of Shingle Vent II for that type of application by cutting it in half length-wise and then covering it with a new fascia board and the upper low slope roof sheet metal counter-flashing.

Now, Smart Vent from DCI Products Inc. makes a product that would work, so i would purchase that instead of doing it my old way.

Ed


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## Ed the Roofer (Jan 27, 2007)

Here are some photos.


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## 1971Mansard (Jun 15, 2010)

Thanks Ed the Roofer. Great Pictures. 

What are your thoughts on the Roofing Contracter I talked to saying that attic ventilation will not help lower the temperature in my house? He says I need a dedicated AC unit. I live in Kentucky... I have already shut off all of the vents in my basement and it was still 82 F in my house when I got home last night.

Thanks,
Brian


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## Ed the Roofer (Jan 27, 2007)

The 2 elderly women who live in that home could not even go upstairs due to the extreme heat issues they experienced.

But, if you noticed, the top roof was a flat roof versus a sloped shingle roof. We installed a white thermoplastic single ply Duro-Last membrane roof on that instead of the previous black hot asphalt roof material they had, which had to decrease the heat absorbtion significantly.

But, all in all, the comfort factor that the two women enjoyed after we did their roofs completely enhanced their living comfort conditions tremendously.

Ventilation and color of the roof surface, as long as it is not black will do you plenty of good.

I am glad you like the photos!!! 

Ed


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## igneous1 (May 6, 2010)

Brian, I'd add this type of radiant barrier: http://www.atticfoil.com 
If you have access into attic, all you need is a staple gun to put this up along the rafters. I did our house last year in the fall and it's made a world of difference. Also add more insulation in your attic...6" just isn't enough. The great thing about the foil is that the attic stays cooler, so your ductwork is cooler. Another thing I'd consider, for summer anyway, is getting solar screens installed. Easy DIY since all your windows look the same size. Your main goal should be keeping heat out because this will ease load on your a/c. My attic never gets over 115*


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## Yoyizit (Jul 11, 2008)

This link, if it will open, will tell you how many BTUs are giving you your 82F
http://en.wikipedia.org/wiki/R-value_(insulation)
You need to know your attic temp and the sq. ft. of the ceilings of the rooms that interface with the attic temp.

Knowing your attic temp, with this link you can figure the effectiveness and cost for various methods, including adding an AC.

The attic temp would have no effect on the room temp if
both were at the same temp or
the room ceilings were perfectly insulated.


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## 1971Mansard (Jun 15, 2010)

Really like the idea of the radiant barrier and adding the insulation. Still does't resolve my lack of ventilation. 

I am thinking I can lower my static vents (4) on the roof and then replace two of the static vents with attic fans or Whirlybird turbines, and cover the other two.


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## Yoyizit (Jul 11, 2008)

"
How much attic ventilation is required to provide proper temperature and moisture control? A number of studies sponsored by federal energy funds are under way to look at ventilation rates and methods. However, several studies previously made can help with this decision. The maximum ventilation rate is required to remove heat during the summer cooling months. Attics can reach temperatures of 150 to 160 degrees F during a summer day, although outside air temperatures are only 95 to 97 degrees F. The cooling load for a home air conditioner depends on the difference in temperature between the inside and outside air, and reduction of attic temperatures from 155 degrees to 105 degrees F will result in a significant reduction in cooling load. In a home with poor ceiling insulation, heat movement through ceilings may account for 30 percent or more of the total cooling cost. With a well-insulated ceiling, this source of heat may account for only 12 to 15 percent of the total cooling cost. Thus, high attic ventilation rates are most important for poorly insulated ceilings. A poorly insulated ceiling is one whose R rating is less than 14 or one with fewer than 4 inches of fiberglass, rockwool or cellulose insulation.

. . .on a July day in Texas, a ventilation rate of one air change per minute [*60 per hour?*] for a typical attic using 95-degree F air will lower the peak attic temperature to about 101 degrees F. Providing half air change per minute will lower the temperature to about 106 degrees F. Thus, the first half change per minute is most effective and a doubling of this rate only achieves about 5 degrees F additional cooling. Studies indicate that further increases in ventilation are not effective in significantly reducing attic temperatures."


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## igneous1 (May 6, 2010)

I'd do what Ed said and install continuous ridge vent. You can also put a box fan or any type of house fan on a timer in your attic and let it push air up thru vents. This is what I've done in my attic, as it is quieter than a big, roof-mounted exhaust fan. Also easier to replace once it dies. Good luck!


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