How we build our homes, both in design and choice of materials, is one of the most significant ways that we can affect our future.
What is Green Living?
Sustainable living refers to a lifestyle that attempts to reduce an individual's or society's use of the Earth's natural resource. Practitioners of sustainable living often attempt to reduce their carbon footprint by altering methods of transportation, energy consumption and diet.
The practice and general philosophy of ecological living is highly interrelated with the overall principles of sustainable development.
The reason for building greener homes is really quite important. We need to live more lightly on the earth, because the degradation of our environment is compromising not only our survival, but the survival of most other living beings on the planet. We can no longer ignore the impact we have on the earth's ecosystems. The way we live, the choices we make in providing for our needs, will have an enormous influence on the quality of life of those who will follow us. Now is the time to take responsibility for the consequences of our life styles!
What is a High Performance Home?
Such a home will come with a higher price tag. But it shouldn’t cost more to own.
The twelve steps to higher performance are as follows:
1. Systems integrated design. During the design stages, the typical home must be reviewed and re-engineered on paper to meet the listed performance goals.
Typically, designs are modified to integrate mechanical system requirements with structural and architectural needs. This is the time to think “house as a system.”
2. Modeling, analysis and equipment sizing. While the home is still just on paper, it must be analyzed to make sure that it will meet the high performance objectives.
3. Higher insulation levels, properly installed. To achieve a 40% savings, higher than normal levels of insulation are essential; however, since house tightness and higher HVAC equipment efficiency are other means to achieve the savings target, the R-values in Table 1 are recommendations, not requirements. The recommendations vary moderately between mountains and plains climates. Just as important as R-value is proper installation of all insulation products. All cantilevers and floors above garages must be completely filled with insulation. Blown-in or sprayed insulation systems are recommended.
4. Solar-smart windows. To improve comfort, reduce equipment sizes and save energy, low-e windows are required. For climates with fewer than 7000 heating degree-days, a home’s windows should have a U-value of 0.35 or lower, with a Solar Heat Gain Coefficient of 0.40 or less. For the mountains, a U-value of 0.32 is required; SHGCs higher than 0.40 are encouraged since solar heat gains reduce the higher heating loads in mountain climates.
5. Tight construction. Air leakage testing with a blower door should indicate no more than 0.22 natural air changes per hour of leakage (roughly equivalent to 0.25 cfm/ft2 of envelope surface area). This is just over 50% tighter than the average new Colorado home being built today.
6. Bulk water management system. As described in EEBA’s new Water Management Guide, “the fundamental principle of water management is to shed water by layering materials in such a way that water is directed downwards and outwards of the building or away from the building.” To provide durability and reduce the potential for mold, a drainage plane covering walls is required for building durability; the drainage plane incorporates appropriate flashings around rough openings and at component intersections. The foundation must include a positive slope to facilitate surface drainage, a capillary break over the footing to prevent moisture movement up into the foundation wall, plus perimeter footing drains that provide positive drainage to either daylight or an accessible sump.
7. Water vapor management. To reduce vapor transport by air movement from the interior into wall and ceiling assemblies, an interior air barrier is required; secondary air barriers that limit wind washing from the exterior are optional. As part of the air barrier system, a durable air barrier must be installed against the framing that will be adjacent to tubs, showers, fireplaces and entertainment centers, plus in ceilings above dropped soffits and within floor systems interior to rim joists. In the mountain zone, a vapor retarder is also required to reduce vapor movement across the wall assembly. In all locations, dirt floors in crawl spaces need a continuous (sealed) impermeable ground cover that serves as both an air and vapor barrier.
8. Controlled ventilation. Mechanical ventilation must be provided. It should be sized to supply 10 cfm per bedroom plus an additional 0.01 cfm per square foot of conditioned space. If the ventilation system fails, there must be a positive indicator that alerts homeowners (e.g., red light at a panel). Intermittent ventilation is essential for baths (50 cfm) and kitchens (100 cfm).
9. Safe and efficient appliances. All combustion appliances must have the by-products of combustion isolated by either power venting, direct venting, or sealed combustion. Furnaces should have minimum 90% AFUE ratings. The water heater’s Energy Factor should be either above EF-0.60, or should have extra tank and pipe insulation added to achieve at least this level of performance. Other supplied appliances should meet the EPA’s Energy Star criteria.
10. Properly sized HVAC equipment with designed and sealed ductwork. HVAC equipment must be sized to be no larger than ACCA Manual J calculations would indicate; as that calculation system is generous, no upsizing fudge factor for temperature setback is needed. Ducts should be designed based on room-specific load calculations (ACCA Manual D). Ducts must be sealed with a durable sealant product--a water-based mastic, butyl tape, or an aerosolized sealant system. Measured duct leakage must not exceed 10% of total system flow; this means building cavities can’t be used for return-air ducts. Ducts against exterior walls or within attics require 100% of the component’s insulation R-value between the ducts and the exterior.
11. Efficient use of building materials. Use engineered lumber instead of dimensional lumber for floor joists and roof framing materials. Use advanced framing that incorporates at least 24-inch o.c. spacing, in both exterior and partition walls.
12. Performance testing. In 1980, an official with the New York State Energy Research and Development Agency stated, “you get what you inspect, not what you expect.” It’s just as true today as it was 22 years ago. Minimum performance quality control includes testing for house tightness, duct tightness, total airflow through the HVAC equipment, and room-to-room house pressures (no more than 3 pascals of difference between rooms, with doors closed). At the end of the day, a fundamental principle consumers must also grasp is that a high performance home will cost more to buy, but not necessarily cost more to own. Utility savings will help offset most or all of the higher mortgage payment. But owners walk away with a better product and builders make more profit with fewer callbacks and less liability. What’s not to like?
