Defining Green in today’s Home Building Marketplace

Defining Green in today’s Home Building Marketplace

As we all know the term “Green Building” is the talk of the industry. Unfortunately, the term is constantly being redefined by every company who is attempting to capitalize on the latest craze.  An effective implementation of all Green building strategies requires a complete understanding of the various components that together make up a viable “Systems” approach to building. Once we understand that every component within the building is dependent on some other component we are on our way to really making a difference.

The early creators of the Green movement clearly identified the most important aspects of a truly “Green Built” home was that it must substantially reduce it’s carbon foot print, it should be constructed in a way that  increases the durability or life expectancy of the structure and that the indoor environment should be a healthy place for humans to occupy. None of these aspects can be addressed unless we first improve the thermal building envelop. A superior thermal envelop provides many benefits and resolves many issues that cause building failures in today’s homes. Improvements in this area provide the highest ROI (return on investment) for the homeowner and the largest reduction in the carbon footprint of the home.  The reduction in the carbon footprint of a home is the single most important aspect when building green and should have the highest level of importance when it comes to setting priorities for improvements to any green building structure.

One example of an incorrect priority is when homeowners spend $8,000 to $12,000 on a solar hot water system when domestic hot water only accounts for 8%-12% of the total energy usage of the home.  Another example would be to pay three times the cost of a conventional HVAC system for a GEO thermal HVAC system and again makes no improvements to the thermal envelop.

While each of these systems can provide a reduction in the energy usage of the home, their impact is significantly less than it could be.  We should first focus our attention on improving the home’s thermal envelop and only then consider additional alternative technologies to further enhance the energy efficiency of the home.  This approach is very much like “keeping the horses in front of the buggy” instead of the “buggy in front of the horses”.

To truly build a “Green” home it must be constructed using techniques that will make it extremely energy efficient and durable. The more energy efficient and durable it is the more green it becomes. The longer a home last the longer the amortization period is for the home, consequently increasing the value from the beginning.  According to several independent studies which include the United States EPA and DOE, building envelop air leakage accounts for 40% - 50% of the heating and cooling cost for a typical home. If you are planning on building an energy efficient durable home you should first look at ways to improve the thermal envelop and reduce the air leakage rate of the home. There are many products on the market today that can address this issue; however none of them will work unless they are installed correctly. This is the biggest issue I see in the field today when inspecting homes for green certification.  To avoid this issue consider using products that inherently provide superior thermal performance by restricting air movement through the building envelop.

In the building science arena, we use the term “Build it tight and ventilate right” with almost every breath we take. Don’t believe the stories about homes being to tight, building science has come a long way. We now know that the indoor air pressure needs to be balanced with outdoor air, and that indoor-outdoor air should be exchanged frequently. The key point here is that unless you create air sealed envelop you cannot control the airflow through the building envelop. When we build it tight and manage the fresh air exchanges we can then begin to design the correct indoor environment providing an energy efficient, durable and comfortable home.

Certain practices will assist in making a home truly “Green” at little to no additional cost:

• Exteriors - Ensure every seam in the house wrap is taped when using a fibrous insulation material. Ensure all fibrous insulations are encapsulated on all six sides with an air barrier or solid material, such as OSB or drywall. Seal all exterior penetrations with expanding foam or flexible caulk.
• Doors and windows- Seal around them with expandable foam and/or sealing tape and keep threshold tolerances tight. A 1/8” gap below an exterior door is equivalent to a 4” hole in your wall.
• Chimneys - Bridge the gap between the framing and fireplace using sheet metal, caulked in place with heat tolerant caulking.
• Ducts - Seal ductwork tightly, especially in attics or unconditioned spaces.
• Add mechanical ventilation in the form of positive pressure ventilating air cyclers or energy recovery ventilators.

The use of advanced building products and techniques will increase the energy performance and durability of the home. In several instances the additional cost associated with these techniques and products can be offset from capital reductions in other areas of the building.

Advanced techniques and products to consider

• Advanced Framing

o   There are several concepts to consider and not all of them can be used in every situation do to structure load requirements.  Making changes to the way in which we frame exterior and interior walls can save you 10%-30% off the normal lumber package price.

• Use Spray Foam or Blown- in  insulations types

o   There must be a zero gap tolerance when using fiberglass batts, and we all know how difficult that can be when working with perfectly shaped insulation materials.  Consider spray foams first because they also reduce air infiltration. The stated R-value of a material is not necessarily the performance R-value.  Spray foam performance is actually much higher than the stated R value of the foam, because of the reduction in the convective loop process that occurs within all fibrous insulating materials. Since all spray foams help reduce or eliminate the convective loop process their performance R is much higher than the stated R value.

• HVAC right sizing

o   Ensure the HVAC contractor you choose performs a Manual J loads on every house, using accurate building specifications and by someone who has been properly trained to perform the load. Reductions in the total HVAC tonnage required for the house can save you several thousands dollars, to be used in other areas of the home.

In summary, there are many opportunities available for you to investigate and consider. What is most important is that you prioritize them according to their impact. Builders and homeowners new to green building often focus immediately on “deep green” technologies such as photovoltaic’s, solar and geo thermal HVAC systems. But the most important choices that can make a house green happen far earlier in the building process and usually provide a bigger impact for much less cost.

Bio

Scott Nichols is the Principle Green Building Consultant of Environmental Resource Partners, Inc. He is a certified ResNet Green Rater, EarthCraft House Technical Inspector and USBGC LEED H certified program manager and inspector.  Last year his company was awarded the Green Advocate and For Profit Education program of the year by the USGBC and the Charlotte Business Journal.  He provides Green Building training sessions to Architects, Builders, local HBA and homeowners.  He can be reached at 704-596-0055 or scott@enviroresourcepartners.com