In recent newsletters, we’ve talked about our commitment to ensure that your log home is as energy efficient as possible. There are two basic compliance paths (the prescriptive approach and the simulated performance alternative) used to ensure energy efficiency as well as compliance with the new federally mandated 2009 IECC (International Energy Conservation Code). Click here for a review of the new IECC regulations.
How is 2009 IECC compliance measured?
There are two ways that compliance with 2009 IECC can be measured: the prescriptive approach and the simulated performance approach. The prescriptive approach is the simplest way to demonstrate compliance with the code. The simulated performance approach is more technical. Compliance based on simulated energy performance requires that a proposed design be shown to have an annual energy cost that is less than or equal to the annual energy cost of a standard reference design.
Prescriptive compliance allows the use of an energy compliance program called REScheck. REScheck is a tool made available through the U.S. Department of Energy, which also supervises the Energy Star® rating program for homes.
Through REScheck, the most commonly used pre-construction compliance software, Katahdin is able to design a log home to ensure that it complies with the 2009 IECC codes for the home’s climate zone. IECC has scaled its requirements based on climate zones, moisture and humidity and severity of winters. The zones are numbered 1 through 8. The higher the number the colder the climate, and ultimately the more insulation required by the code. A REScheck analysis will provide state or local code enforcement officers with documentation to verify code compliance.
How does REScheck work?
The REScheck program is based on specific energy code requirements already programmed into the software. Specific energy codes, including the most recent (2009 IECC) are available to test the home design. After opening the program, the designer or architect selects the applicable energy code and then enters specific information about the project being analyzed.
Since REScheck is evaluating the energy efficiency of the home, the information required for an analysis comprises the “thermal envelope” of the home—foundations, floors, walls, and ceilings. The thermal envelope separates heated/cooled (conditioned) space from unconditioned space. First the appropriate building code is selected for the analysis. Then data is entered that identifies the project, including project location, project type (new construction or addition/alteration), building characteristics (1 & 2 family or multi-family), square footage of heated/cooled floor area, and general project details and notes. The home being evaluated is compared against a “baseline” home of the same square footage that meets the minimum code requirements.
The designer then moves through the REScheck program entering information about the thermal envelope including gross area, and insulating values for each component of the thermal envelope (foundations, floors, walls, and ceilings). The designer also enters the area and insulation values of each exterior door, window and skylight. For log homes, REScheck also requires the user to select the wood species of the logs used in the walls, as different log species have different insulating properties. Both below grade and above grade walls are included in the analysis if they are enclosing heated/cooled areas.
One element that has changed in the most recent updates to the energy code (IECC 2009) relates to the mechanical equipment, such as the furnace, boiler, heat pump, and air conditioning unit. Prior to IECC 2009, code compliance allowed for a trade-off between insulation in the envelope and the mechanical components. For example, a high-efficiency furnace could offset a lower, non-compliant R-value in the walls of the home. The energy code no longer allows mechanical trade offs. Therefore, the thermal envelope must conform to a higher standard.
When Katahdin developed the exclusive R-23 Energy Envelope System, we sought and received professional opinions from the developers of REScheck and 2009 IECC to ensure that this high-efficiency insulation system would meet the intent of of the new standards.
The IECC 2009 energy code also includes several mandatory requirements, such as, air leakage requirements, recessed lighting requirements, fenestration (doors and windows), fireplace requirements, mechanical system requirements, snow melt system requirements, pool requirements, fireplace requirements, and general lighting system requirements that apply to all residential buildings.
The REScheck program consolidates all of the information entered and arrives at a percentage by which your project “passes” or “fails” the selected energy code. The REScheck analysis indicates whether the combined energy efficiency elements of the home meet or surpass the minimum requirements of the baseline home. As there are so many variables to individual homes, you may find that some tweaking is necessary for your home design to meet code requirements. In some instances, a small change in window areas can effect a sufficient increase in a REScheck score.
REScheck allows you to print out three different certificates: a compliance certificate, an inspection certificate, and a “panel” certificate (aka: energy efficiency certificate). REScheck is not a tool that you’ll need to learn yourself, but it is a very useful way for Katahdin’s design team to ensure your log home has the best possible energy efficiency.