Sunday, August 28, 2011

THE ERV - What the heck is an ERV?

The ERV - What the heck is an ERV?

One of the criteria for finding property was being 3000 feet above sea level so our house might be cooler in the summer months. Our chosen home site is at about 3500 feet and since we have been on site these last couple of summer months we have noticed a definite temperature difference at lower elevations. We have noted between 5 to7 degrees cooler than the posted highs for the city of Asheville. That can make a big difference when the highs are in the nineties. Our plan is to try to live and work without having an air conditioning system installed.

These are some factors that may help us with this goal.

  1. Edrianna and I have conditioned ourselves to tolerate moderate temps by having our house thermostat in Florida set at 78 degrees during the summer months. This was an idea that the government tried to mandate years ago for commercial buildings and nowadays suggests for residential users to save energy. This is a great idea and has saved us a lot of money in electric costs over the years.
  2. Our new house has good exposure for capturing outside air with large windows around the perimeter of the house.
  3. The house will be insulated to the max and have a metal roof that will reflect heat back up to the sky.
  4. Even on hot days the temperature drops to very comfortable levels at night in the mountains of North Carolina provided you have a way to exhaust the hot air that builds up in the house.

This leads us to the systems we are installing to ventilate the house. The low tech way is to open two windows on opposite sides of the house and put a fan facing outward in one of them. This creates a vacuum effect that removes the stale hot air and replaces it with cooler fresh air (provided the outside temp is lower than inside). This is quite effective and is what we did growing up in the good old days sans air conditioning. My first choice would have been a whole house fan that installs in the ceiling to exhaust air into the attic and then makes its way outside through roof soffit and ridge vents. We are going with spray foam insulation in the roof and a new trend of NO VENTS, so we can’t do this method. (I’m trying to obtain more information about the benefits and pit falls of having a vented or un-vented roof. Some say it is best and some say it isn’t. I will keep you posted.) Here are our solutions:

  1. Two highly efficient bath fans that will act as whole house fans ventilated outside using duct work. If we open a window the vacuum effect will happen to exchange air. This method will not move as much air as a large fan put will have a positive effect.
  2. We are installing an ERV which sounds like something left over from the Apollo space missions. It is an Energy Recovery Ventilation system or whole house ventilation system. This helps to exhaust stale air from the house and draw in fresh air. We plan on using this in the same way as the bath fans. I am not sure how effective this will work because they are traditionally used in conjunction with air conditioning systems. The major benefit of this devise is that it will provide fresh healthier air, eliminate odors and dilute indoor pollutants. This system works best when the windows are closed and is actually more beneficial in winter when the house is sealed up for long periods of time. The ERV also has a heat recovery system so the warm air inside will not be lost during air circulation.
Rick Cooper from Mountain Air Mechanical Contractors met with Al and I one day to walk through the house and discuss installation. Morat and Igor arrived a few days later to install the system and duct work. They also installed the duct work for all the bathroom fans and laundry room dryer.
Igor installing the ducts coming from the basement.

The ERV!

Duct work.

ERV ceiling register (vent) - sealed and ready for a pressure test.

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