MY Energy Efficiency.info

A well sealed house might have .5 natural Air Changes per Hour (nACH). This is the volume of air that moves into and out of your house in 1/2 and hour. You could equate it as having to reheat or cool all the air in your house every 2 hours. Next time you have to dust your house, remember that about an hour ago, halve of the dirt on that dresser was outside your house. If you tighten the house up to less that .37 nACH, you start to have Indoor Air Quality problems in the house.

An Energy Star house or generally houses built to the 2006 International Residential Code (IRC) might have about .65 nACH. Homes built before 1980 could have 1 - 1.5 nACH. Older houses will probably have higher values. The hidden penalty in the Air Changes in a home is the moisture content of the air that is coming into the house. Moisture laden air must be dehumidified as it is cooled. Up to 50% of the sizing of your Air Conditioner may be needed just to handle the dehumidification in coastal and high humidity areas of the country.

Weatherization is the process of tightening up the building envelope to reduce air infiltration into your house. The typical house has the equivalent of a 2 - 4 square foot hole in one of the walls of your house. You can't see it, but energy in flowing into and out of that hole 24 hours a day. With the air comes moisture in the form of humidity that must be removed as the air is conditioned (heated or cooled). This "hole" is the sum of all the little gaps, crack and crevices that exist at your building envelope. For most people the envelope for their house is the sheetrock or interior wall surface. Newer houses moves the building envelope towards the exterior surfaces of the house to minimize the effects of water vapor in the conditioned part of the house. Existing houses can move the envelope towards the exterior wall by air sealing the exterior, but there will always the pathways within the structural members that can not be sealed after construction, so they will never reach the potential savings of weatherization that a post 2000 constructed house can achieve.

The homes we live in leak air pretty badly. If you tighten up the building envelope to much then the indoor air becomes toxic and it can have adverse health affects on the occupants. The trick is finding a cost effective balance between loosing energy from cracks and gaps in the building envelop and a tight house that will make you and your family sick. The most efficient home improvements in reducing your energy consumption are also the cheapest.

Any improvements in sealing the building envelope will help reduce the flow of air and moisture through your home. Use a good quality sealant around all exterior and interior wall penetrations. Install wall outlet and switch gaskets through out the house. Install new weather strip around your doors and windows. Heating and Cooling ducts in the attic or foundation crawlspace typically leak 25% of all the energy spent heating or cooling all the air flowing through that duct. Tighten the duct joints up with straps and mastic. Make sure a rubber gasket is installed on the HVAC register in the house.