Energy Efficiency in New Homes is about both comfort and money savings.
New Homes Gain Energy Efficiency with Low-E Windows
Energy Efficiency features in a home make it both comfortable and save money. Who has stayed as a guest in someone’s house and when they closed the bedroom door for privacy noticed the room felt stuffy when the rest of the house was at a comfortable temperature? Or perhaps been sitting in an older home near a window and actually felt a draft in the proximity of the window. New Homes today are, overall, much more efficient than they were a few years ago. One of the most popular energy efficient features in new homes today is “low-E” glass windows. This type of window contains one ore more extremely thin layers of metallic particles which filter out the heat (long wavelengths) while allowing the visible light spectrum (short wavelengths) to enter. In the winter, the low-E glass reduces the heat loss in your home. Not all low-E windows are suitable for the Southern Climate Zone, which San Antonio is located in. The Energy Star Web Site provides information about high performance windows.
New Homes contain low-E energy efficient windows which improves home comfort.
Windows are rated by a U-factor which refers to the insulating quality and SHGC, which refers to the reflecting quality of keeping heat out. Windows are further designated by low E-2, or low-E-3. Since windows account for about 30% of the energy consumed in a home, it helps to have Energy Star qualified windows. A window with a rating maximum U-Value of 0.40 and a maximum SHGC of 0.25 would be superior to one with a Maximum-Value of 0.60 with a maximum SHGC of 0.27.
Advanced Framing Techniques
Some new home builders use advanced framing techniques to reduce construction waste and enhance energy efficiency of the home.
According to David Weekly Homes, wood is a poor insulator (R-5) compared to wall insulation. Advanced framing allows the placement of insulation in areas that were previously blocked by framing lumber. Framing is done with 2X6 studs on 24″ centers (in lieu of 2×4 on 16″ centers) Stacking roof rafters and joists directly over wall studs transfers the load directly downward, making a stronger load. There are other advantages of this technique. Not only are the walls thicker and more insulated, the home is quieter. The idea with high performance windows and with advanced framing techniques is to create a tighter building envelope so heating and cooling systems do not have to work so hard. Alternatives to Advanced Framing techniques involve pairing a stick framing (2×4’s) with spray foam insulation.
New Homes have an exterior skin, “sheathing,” that can offer no insulation or can offer an R-3 insulation, for example.
Energy Efficiency through Sheathing
Sheathing is used behind siding, rick or stone and contributes to a tighter building envelope. This area of construction is evolving with the goal of creating better air barriers and lasting results. As with all products, correct installation is essential. If the product needs to be taped, then the seams need to be correctly taped.
Air Conditioners Must be Right Sized
Air conditioners that are installed based solely on the square footage of a home may undermine the energy efficiency of that home. ACC Manual J sets out the variables that influence the choice of an HVAC system and those variables include: roof color, radiant barriers, type of windows, amount of shade, and more. An over-sized air conditioner may cause the home to feel clammy because the AC unit cycles on and off and does not properly dehumidify the air. Air conditioner units come with SEER ratings. The bar keeps getting raised as to what number represents a high efficiency unit. In Fall 2014, a 16 SEER system would be considered awesome. The minimum SEER rating for new AC units mandated by the federal government in 2006 is SEER 13. An AC unit is really a system that consists of an outside condensing unit and interior unit that has an air supply, furnace blower and air ducts. The system efficiency depends on all those parts being compatible with each other and with other parts of the house. For example, if a new home were under construction and the home buyer decided to change the type of attic installation from batt to foam, that would influence the air conditioner choice as well as the ventilation in the attic. A SEER 16 rated HVAC unit would not achieve high efficiency if the HVAC ducts located in unconditioned space were not insulated (preferably with R-8 material) or were torn. Simple, programmable thermostats are also useful energy efficient devises. Jump ducts can hep circulate air in rooms where the door is typically closed.
Energy Efficiency Measured by HERS
A HERS rating is the industry standard for measuring energy performance. The higher the score, the worse the rating. If a new home has a HERS score of 70, that means the home is 30% more efficient than a typical new home and way more efficient than a typical re-sale home.