Positive Pressure! Don't Breathe Stale Air - Add a Fresh Air Duct in your Home

adam

Published on 03-02-2010 08:39 PM

2 Comments

I don't think this one is going to save much money, if any, but it's a good idea anyway. So here's what happens:

Your home is built air tight. Or so you think. Now you turn on your bathroom exhaust fan for 10 minutes and blow a few hundred cubic feet of air out of the house. Then you turn on your kitchen down draft and blow another 1000 feet of air out. Then some hot air rises through the crack where your attic door comes down and escapes into the attic. So what is happening in your house??? It's like sucking the air out of a balloon. The air pressure in your house becomes lower than the air pressure outside. This is called negative pressure. So for most houses, even the "air tight" ones, you will pull in outside air through little cracks around doors, windows or even baseboards to offset the negative pressure. This is unconditioned air that is either too hot, too cold, too humid or too dry. Maybe the really really air tight houses can combat this slightly, although having a totally air tight house is unhealthy for other reasons.

So now you have outside air coming in from various spots. In the summer it is hot and humid and in the winter it is cold and dry. Not good for trying to keep your house comfortable.

Here's the solution. Add a small duct to your existing HVAC unit to pull in a very small amount of fresh air. This air is immediately run through your HVAC unit, conditioning the air, but creating positive pressure in the house. Now instead of pulling air in through the cracks, you are pushing air out through the cracks, if anything. You might be thinking it's the same either way, but creating positive pressure has some advantages that I'll list below:

1. Positive pressure brings in fresh air that is immediately conditioned by your HVAC system.
2. You know that you are always exchanging some air in the house. Homes that are built too tightly can get stale air that is unhealthy to breathe.
3. You can help avoid radon in the basement. Radon builds up because the pressure of the soil around the basement is higher than the pressure in the basement. The radon actually seeps into your basement from the soil through your basement walls. Creating just a bit of positive pressure has proven to eliminate radon in most cases.
4. You can control how much fresh air you bring in. Look at something like www.aircycler.com that will control how often your HVAC fan will come on throughout the day and how often the fresh air duct will be open during that time.

Another option if you live in a very humid climate is to add a fresh air duct in conjunction with a dehumidifier. This ensures that the air you bring in isn't too humid and keeps the whole house more comfortable. This costs money to operate, but may allow you to keep the temperature a few degrees higher and still stay comfortable which can save you money overall..

Does your house have a fresh air duct? If so, how did you set it up and how is it working?

_{This article was originally published in forum thread:

Positive Pressure! Don't Breathe Stale Air - Add a Fresh Air Duct in your Home
started by
adam} _{View original post}

Categories:

2 Comments

batticdoor - 03-03-2010

How To Reduce Your Energy Bills / Energy Conservation Begins at Home

Imagine leaving a window open all winter long -- the heat loss, cold drafts and wasted energy! If your home has a folding attic stair, a whole house fan or AC Return, a fireplace or a clothes dryer, that may be just what is occurring in your home every day.

These often overlooked sources of heat loss and air leakage can cause heat to pour out and the cold outside air to rush in -- costing you higher heating bills.

Air leaks are the largest source of heating and cooling loss in the home. Air leaks occur through the small cracks around doors, windows, pipes, etc. Most homeowners are well aware of the benefits caulk and weatherstripping provide to minimize heat loss and cold drafts.

But what can you do about the four largest “holes” in your home -- the folding attic stair, the whole house fan or AC return, the fireplace, and the clothes dryer? Here are some tips and techniques that can easily, quickly and inexpensively seal and insulate these holes.

Attic Stairs

When attic stairs are installed, a large hole (approximately 10 square feet) is created in your ceiling. The ceiling and insulation that were there have to be removed, leaving only a thin, unsealed, sheet of plywood.

Your attic space is ventilated directly to the outdoors. In the winter, the attic space can be very cold, and in the summer it can be very hot. And what is separating your conditioned house from your unconditioned attic? That thin sheet of plywood.

Often a gap can be observed around the perimeter of the door. Try this yourself: at night, turn on the attic light and shut the attic stairway door -- do you see any light coming through? These are gaps add up to a large opening where your heated/cooled air leaks out 24 hours a day. This is like leaving a window open all year round.

An easy, low-cost solution to this problem is to add an attic stair cover. An attic stair cover provides an air seal, reducing the air leaks. Add the desired amount of insulation over the cover to restore the insulation removed from the ceiling.

Whole House Fans and AC Returns

Much like attic stairs above, when whole house fans are installed, a large hole (up to 16 square feet or larger) is created in your ceiling. The ceiling and insulation that were there have to be removed, leaving only leaky ceiling shutter between the house and the outdoors.

An easy, low-cost solution to this problem is to add a whole house fan cover. Installed from the attic side, the whole house fan cover is invisible. Cover the fan to reduce heating and air-conditioning loss, remove it when use of the fan is desired.

If attic access is inconvenient, or for AC returns, a ceiling shutter cover is another option for reducing heat loss through the ceiling shutter and AC return. Made from R-8, textured, thin, white flexible insulation, and installed from the house side over the ceiling shutter with Velcro, a whole house fan shutter cover is easily installed and removed.

Fireplaces

Sixty-five percent, or approximately 100 million homes, in North America are constructed with wood or gas burning fireplaces. Unfortunately there are negative side effects that the fireplace brings to a home especially during the winter home-heating season. Fireplaces are energy losers.

Researchers have studied this to determine the amount of heat loss through a fireplace, and the results are amazing. One research study showed that an open damper on an unused fireplace in a well-insulated house can raise overall heating-energy consumption by 30 percent.

A recent study showed that for many consumers, their heating bills may be more than $500 higher per winter due to the air leakage and wasted energy caused by fireplaces.

Why does a home with a fireplace have higher heating bills? Hot air rises. Your heated air leaks out any exit it can find, and when warm heated air is drawn out of your home, cold outside air is drawn in to make up for it. The fireplace is like a giant straw sucking the heated air from your house.

An easy, low-cost solution to this problem is to add a fireplace draftstopper. Available from Battic Door, a company known for their energy conservation products, a fireplace draftstopper is an inflatable pillow that seals the damper, eliminating any air leaks. The pillow is removed whenever the fireplace is used, then reinserted after.

Clothes Dryer Exhaust Ducts

In many homes, the room with the clothes dryer is the coldest room in the house. Your clothes dryer is connected to an exhaust duct that is open to the outdoors. In the winter, cold air leaks in through the duct, through your dryer and into your house.

Dryer vents use a sheet-metal flapper to try to reduce this air leakage. This is very primitive technology that does not provide a positive seal to stop the air leakage. Compounding the problem is that over time, lint clogs the flapper valve causing it to stay open.

An easy, low-cost solution to this problem is to add a dryer vent seal. This will reduce unwanted air infiltration, and keep out pests, bees and rodents as well. The vent will remain closed unless the dryer is in use. When the dryer is in use, a floating shuttle rises to allow warm air, lint and moisture to escape.

If your home has a folding attic stair, a whole house fan, an AC return, a fireplace, and/or a clothes dryer, you can easily, quickly and inexpensively seal and insulate these holes.

Mark D. Tyrol is a Professional Engineer specializing in cause and origin of construction defects. He developed several residential energy conservation products including an attic stair cover, an attic access door, and is the U.S. distributor of the fireplace draftstopper. To learn more visit Weatherization Home Energy Star Conservation Insulation Products

Reply