Has Anyone Built an Outside Air Ventilator?

[Axaday]

I noticed yesterday evening that my inside temperature was 80, which is where my thermostat is set, but it was 76 outside. It made me wonder if I could build something to trade for outside air. Maybe with a second thermostat?

I know that the simplest thing is to open a window, but I actually have a lot of outside allergies at this time of year and would rather be able to HEPA filter the air.

[saunders1313]

I know some central a/c units do have fan settings, I would think that it would draw air from outside for that.

[PaleMelanesian]

mmmm... nope. They just circulate the air. In at the unit, wherever the filter is, and out the ducts.

I've thought about this myself. I'm concerned about humidity, especially inside the ducts themselves. You don't want mold growing there.

[rgathright]

Actually, if the inside of your house is hotter than the air outside this is a sign that you are getting to much sun inside your house. Try adding some retractable sun shades or curtains over any east or west facing windows.

To see if this will make a difference hang a large sheet over any window where you can feel heat from the light coming in. It may look unattractive but it can help you guage whether adding shades is worth the $$$ and effort.

Below is an example of the shades I put in my house. I have reduced my home utility bill by about 10% in the last two months with $500 worth of wooden/bambo shades. The shades also gave my house an updated look which several guests have commented on!

[beatr911]

What you are describing in HVAC trade terms is an "economizer" setting. In many HVAC designs for larger (and some smaller) buildings when the outside air is cooler than inside air and the themostat calls for cooling, the controls will simply open dampers to simply exchange outside air for inside air. Often this happens in the evening.

Most residential systems use 100% recirculated air, but if you find a competent HVAC contractor willing to work with you a residential system could be configured.

Cheaply, you could tape a HEPA filter on a box fan, place it in a window and blank off the rest of the window. Just depends on how much ghetto you're willing to live with.

[cfg83]

beatr911 -

Originally Posted by beatr911

What you are describing in HVAC trade terms is an "economizer" setting. In many HVAC designs for larger (and some smaller) buildings when the outside air is cooler than inside air and the themostat calls for cooling, the controls will simply open dampers to simply exchange outside air for inside air. Often this happens in the evening.

Most residential systems use 100% recirculated air, but if you find a competent HVAC contractor willing to work with you a residential system could be configured.

Cheaply, you could tape a HEPA filter on a box fan, place it in a window and blank off the rest of the window. Just depends on how much ghetto you're willing to live with.

That's what I was going to suggest. It could be a backyard window so it wouldn't be so blatant.

We have a < 1000 square foot house, so we only have an 18K BTU wall A/C. Here are our old-school controls :

ac_fan_mode.jpg

CarloSW2

[rgathright]

I suggest putting an automatic dehumidifier in the room incase the humidity of the air coming in is higher than that of the house.

[Axaday]

Originally Posted by rgathright

Actually, if the inside of your house is hotter than the air outside this is a sign that you are getting to much sun inside your house. Try adding some retractable sun shades or curtains over any east or west facing windows.

All of my windows have drapes blocking the sun all the time. It is after dark that this situation arises because the inside of my house doesn't shed heat as fast as the outside does when the sun goes down.

I may go the official HVAC route or at least talk to them. I will not be doing any more business with the people who installed my current system, but there is another company in town that sells another brand of the exact same equipment.

My house is pretty comfortable at 80 because my central unit has a dehumidifying mode that it goes into after it gets to the temperature setpoint and when it dries the air out it feels a lot cooler than it is. But all the same, I would gladly take 76 if it was free.

Edit - Does anyone know how these work? http://www.bryant.com/products/perfe...s/energy.shtml

[Tony Raine]

what about getting a sheet of that washable hepa-filter stuff and install it in a screen frame? you can get the framing for pretty cheap, and they are easy to cut/put together with the right tools (also cheap).

when you want open windows, just swap in the "hepa-screen"

[beatr911]

To help reduce the energy use of your existing system and anything you add, consider additional insulation, a strategically placed shade tree and/or exterior window valances. I've seen/like solar panels mounted over south side windows to shade the window from summer sun and let in winter sun. This can reduce the heat gain in the afternoons and consequently reduce or eliminate the amount of energy used to cool the house in the evening.

I like the idea of the filter screen replacement. If there is enough breeze in your area, this would be really energy efficient. The HEPA filter media is pretty restrictive.