Need to vent attic for house fan...help.

[Jay Sco]

I was inspecting my attic today in planning for a whole house fan and discovered I don't have a 'traditional' attic vent. I have these little deals all around the eave (eve?) of the house. I don't think they will allow proper ventilation.


I do have a decorative BS type thing where a vent SHOULD be right here.

And a pic from the inside.


My home construction knowledge is pretty limited. I'm thinking just take a sawzall to the damn thing and open it up and put a real shutter type vent in there. Will this cause a collapse of the entire house, or some other misfortune? Or does this sound like a legit idea?

 

[75gmck25]

The vents you have may be marginally enough, but in SoCal I would want a lot more ventilation.

A ridge vent combined with a large number of soffit vents works the best because it encourages natural convection, but I don't know how you use a ridge vent with a tile roof. After I installed a ridge vent on my Texas house I could actually feel a breeze (from convection) going up when I pulled down the attic stairs in the garage.

Opening up the vent you see shouldn't hurt anything, but it looks like the attic might have a vertical brace running right across the opening. You may want to frame around it like a window so that you keep the integrity/strength of the wall.

Bruce

 

[yeldogt]

Why do you want to vent it?

I see the air handler is in the attic -- not the best place for it.

How is the insulation? what is the attic temp?

Attic fans create negative house pressure -- they are energy hogs.

Are you having a problem?

I would add more insulation if you have an issue.

 

[Ray-CA]

Try this site (http://www.roofvents.com/calculator.html) or others like it.

Are you have heat issues? These work very well as long as you have sufficient in-flow.

Ray

 

[Jay Sco]

The vents you have may be marginally enough, but in SoCal I would want a lot more ventilation.

Opening up the vent you see shouldn't hurt anything, but it looks like the attic might have a vertical brace running right across the opening. You may want to frame around it like a window so that you keep the integrity/strength of the wall.

Bruce

I figured on framing around it if that's what it came to. I forget exactly but for a ~3500cfm fan it required around 5 sq ft of vents. Even if all those little holes added up to 5 there is still some weird baffle wall in the attic, never seen anything like it before.

Why do you want to vent it?

I see the air handler is in the attic -- not the best place for it.

How is the insulation? what is the attic temp?

Attic fans create negative house pressure -- they are energy hogs.

Are you having a problem?

I would add more insulation if you have an issue.

Try this site (http://www.roofvents.com/calculator.html) or others like it.

Are you have heat issues? These work very well as long as you have sufficient in-flow.

Ray

I think you two misunderstood. Looking at a whole house fan, not an attic fan.
Like this:
http://www.quietcoolfan.com/qc-3100.html

 

[yeldogt]

Whole house fans don't use vents designed for "attic ventilation" -- they require dedicated vents otherwise you will really pressurize the attic and decrease the flow.

We had a huge one years ago that we opened windows in the attic when we used it - the one at our shore house is hard piped to exterior wall vent.

You can get the vents custom made.

 

[over40pirate]

I assume by whole house fan you mean an attic exhaust fan. I had a house with a big exhaust fan in the attic. With the fan on, and the attic door open, and a window open at the other end of the house, you could feel the breeze. just be careful that the door stop, on the attic door doesn't release. Big bang!

Not sure why an attic fan would not work with a lot of small vents, as opposed to a large vent, if total area is the same. Unless you already have enough vent area, I would put a vent as large as the fan, at the opposite gable.

 

[kbs2244]

Are you a S CAL native?
Construction there is different than in the Midwest.

What kind of problems are you trying to solve?
At the least, I would talk to a local HVAC guy.
He will know the area and the common problems and fixes for them.
Most will work with a DIY guy if you buy the hardware from them.

 

[Maxwell007]

Why do you want to vent it?

I see the air handler is in the attic -- not the best place for it.

How is the insulation? what is the attic temp?

Attic fans create negative house pressure -- they are energy hogs.

Are you having a problem?

I would add more insulation if you have an issue.

Maybe we're talking about two different things here but I live in SoCal in an area where it is really hot. I installed a whole house fan a few years ago and it was the best thing I ever did. If it's an "energy hog" it's much less of a hog than my central A/C unit. After the installation of the fan my bills went down dramatically. I more than paid for the fan in one summer. We open up the house at night, run the fan and come morning, the house is near ambient air temp. Close up the windows, doors, etc. and do not have to use the A/C until very late in the day even on the hottest of days. Very good investment.

 

[yeldogt]

Maxwell007: I thought the OP was trying to vent the attic in my first post ..... with a powered attic fan ... the kind on top of the roof.

 

[tdkkart]

Maybe we're talking about two different things here but I live in SoCal in an area where it is really hot. I installed a whole house fan a few years ago and it was the best thing I ever did. If it's an "energy hog" it's much less of a hog than my central A/C unit. After the installation of the fan my bills went down dramatically. I more than paid for the fan in one summer. We open up the house at night, run the fan and come morning, the house is near ambient air temp. Close up the windows, doors, etc. and do not have to use the A/C until very late in the day even on the hottest of days. Very good investment.

This is exactly the way we use ours, and exactly the experience we have with it. No way can you call it an "energy hog", it does it's job very well and cheaply.

 

[pattenp]

I had a whole house fan in a previous home and my only complaint was it would **** gnats through the window screens into the house.

 

[Jay Sco]

Are you a S CAL native?
Construction there is different than in the Midwest.

What kind of problems are you trying to solve?
At the least, I would talk to a local HVAC guy.
He will know the area and the common problems and fixes for them.
Most will work with a DIY guy if you buy the hardware from them.

The only problem is in the evening it's cooler outside than inside but the air is stagnant, so opening the windows does nothing. A house fan solves this at a cheaper cost than running the AC.

Maybe we're talking about two different things here but I live in SoCal in an area where it is really hot. I installed a whole house fan a few years ago and it was the best thing I ever did. If it's an "energy hog" it's much less of a hog than my central A/C unit. After the installation of the fan my bills went down dramatically. I more than paid for the fan in one summer. We open up the house at night, run the fan and come morning, the house is near ambient air temp. Close up the windows, doors, etc. and do not have to use the A/C until very late in the day even on the hottest of days. Very good investment.

That's exactly what I'm talking about.

I had a whole house fan in a previous home and my only complaint was it would **** gnats through the window screens into the house.

LOL! I'm just getting one big enough for my sq ft, not going crazy with the size.

 

[JoeFin]

Depending on "How many" of the little holes are provided they could be adequate and meet code

BUT The Real Concern is

Your not supposed to turn your attic into a plenum by venting your living space air into it. Once you do that all the applicable building codes go right out the window and you are supposed to use a new set of standards designed to NOT FAN the FLAMES of an ATTIC FIRE

Some thing your building inspector, real estate agent, or home-owner's insurance provider might be concerned over.

You can however use a fan that vents directly to the outside through duct-work

 

[JoeFin]

The only problem is in the evening it's cooler outside than inside but the air is stagnant, so opening the windows does nothing. A house fan solves this at a cheaper cost than running the AC.


That's exactly what I'm talking about.

Yep and its called passive cooling schemes and I helped in designing PLC systems that provided that as well as other automation functions on 500,000 sq ft whare house facilities. And it works very well

What you are looking to do can be automated quite easily with 2 thermostats, a 365 Day timer, and a couple of relays

Set one thermostat outside under the eaves where it will be free from moisture and wind chill. Set the other thermostat inside the house. Set the 365 Day timer along with the relays in a 12 x 12 x 4 enclosure in a closet

You want the timer to begin sampling outside air at 12 midnight (or what ever works for your location) and any time the air outside is below 68 deg and the inside air is above 65 deg start the fan. You will also want to "Lock-out" the heating call on your furnace / air conditioner when the fan is called and keep it locked out for a period of time