Article #1462 - REScheck Webcast Questions - Building Envelope
This article is based on questions asked during both the May 6, 2005
REScheck Training Webcast
and the July 28, 2005
as well as questions received through email following these events. The original language of the questions and answers has been modified to make them as generic as possible while retaining the applicable specific information.
How do you treat an unconditioned room that is optionally insulated?
A space that is considered unconditioned (not heated or cooled) would not be required to meet energy code requirements and the space would not be included as part of the building envelope for compliance, regardless of whether the space is optionally insulated.
The following link offers additional information on this subject:
What is the Building Envelope?
Are spaces over garage areas considered conditioned areas? What about carports?
If you have a room above a garage that is conditioned, the garage ceiling would be considered part of the conditioned building envelope (floor over unconditioned space) and would need to be insulated and sealed according to code.
Occupied living space over a carport would be required to meet the applicable energy code requirements for a conditioned space. The floor of the living space over the carport would be defined as a floor over outside air.
In Texas Gulf Coast areas, recent research indicates that it is not recommended to install a vapor retarder on the warm-in-winter side of non-vented framed ceilings, walls, and floors. Does RES check recognize this regional difference?
RES check will generate an Inspection Checklist based on the code selected, location, building envelope components, and mechanical information entered into the program. Vapor retarders will be listed on the Inspection Checklist if the code and project location are within areas that require vapor retarders. The energy code does have exceptions to installing vapor retarders where in construction moisture or its freezing will not damage the materials, where the county in which the building is being constructed is considered a hot and humid climate and identified as such in the climate zone maps, and where other approved means to avoid condensation in unventilated framed wall, floor, roof and ceiling cavities are provided.
The following link offers additional information on this subject:
The Importance of Vapor Retarders
How do we do the take off of the two family house that is three stories in height and has two furnaces and two air conditioners?
Enter the entire exterior building envelope that would include both family dwelling units. Interior walls and floors that are between two conditioned spaces would not be included in your take offs.
For the HVAC systems, enter each unit separately in RES check . However, if the efficiency of the units is above the minimum efficiencies in the code, RES check will only give credit for the lower efficient unit shown.
How do you find infiltration if the house is not square? Do you just add the total feet of the walls?
Typically, a blower door test is performed to determine the rate of infiltration (air changes per hour). The code has language that defines a workman like installation of sealing measures for penetrations, voids, gaps in the building envelope.
Are multifamily projects (town homes) to be calculated as an overall building or can it be done by individual unit?
Compliance can be calculated either way (as an entire project or individual units). However, showing compliance by each individual unit can be more stringent and time consuming. The complexity is due to the fact that common walls between units cannot be shown as part of the building envelope. Common walls between two conditioned spaces would be considered an interior wall. Therefore, calculating compliance for the overall exterior building envelope would be a simpler approach to meeting code compliance.
How do I enter a basement floor?
For walk out basements, the exposed portion of the slab should be entered in RES check in linear feet with the applicable depth of insulation and R-value. If the slab is not insulated and is considered part of the conditioned building envelope, the depth of insulation and R-value should be entered as zero.
For slabs with a top edge above finished grade or 12 inches or less below finished grade, the IRC requires the insulation R-value to be applied to the outside of the foundation or the inside of the foundation wall (the required R-value of insulation is dependent upon location of the project based on heating degree days). The insulation shall extend downward from the top of the slab, or downward to the bottom of the slab and then horizontally in either direction, up to a minimum distance of 4 feet (total depth of insulation is dependent upon location).
Therefore, a slab that is greater than 12" below grade would not need to be entered in RES check and would not be required to meet slab insulation requirements.