Article #1453 - REScheck Webcast Questions - HVAC
This article is based on questions asked during both the May 6, 2005 REScheck Training Webcast
and the July 28, 2005 REScheck Training Rebroadcast 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.
Do I get added credit for advanced HVAC systems such as ground source heatpumps?
REScheck does not allow tradeoffs for ground source heat pumps, forced hot water, and some other systems in the Mechanical folder. The software does allow tradeoffs with air source heat pumps, fossil fuel furnaces, boilers, and air conditioners.
REScheck makes only the most common equipment types available for tradeoff (those types which are covered by Federal appliance standards and are rated with an AFUE, SEER, or HSPF). Other systems such as radiant floors, geothermal heat pumps, evaporative coolers, and others require complex calculations not available in REScheck. These systems can receive tradeoff credit only through a whole-house performance (i.e., Chapter 4) analysis.
The following links offer additional information on this subject:
- Why is my Mechanical Equipment not Available in the REScheck Software?
- What Should I Do if my Mechanical Equipment is Not an Option in the REScheck Software?
Does the compliance report tell you the heat loss of the building? What about cooling load?
No, because infiltration, duct loss, internal gains, and solar gains are not used in calculating compliance.
The following link offers additional information on this subject:
Does REScheck Take Air Infiltration into Consideration?
Does the code require a high efficiency furnace? I noticed the example showed 78% efficiency.
No, the code does not require a high efficiency furnace. The code does require the furnace meet the minimum efficiency mandated by NAECA which has a 78% efficiency rating.
How do you account for different mechanical equipment types such as split system, RTU etc?
The efficiency tables in the energy code define both split, packaged, and other systems. For systems not shown in the residential sections of the code, the code refers you to the commercial mechanical section.
Can we use lower R-values than required of duct insulation with higher SEER ratings?
There is no tradeoff allowed for duct insulation, therefore, regardless of the SEER rating, the minimum amount of duct insulation dependent upon project location will be required.
If you have a 2 story home and you use a 90% efficient unit on the first floor and use an 80% on the 2nd floor, does REScheck calculate on both systems or does it use only one?
You can enter multiple HVAC systems in REScheck, however, credit towards the building envelope will be taken from the least efficient unit entered in the Mechanical folder.
On a house with an unconditioned basement, can you trade a 90% furnace in the basement for insulation in the attic ceiling?
REScheck does perform equipment efficiency tradeoffs towards the conditioned building envelope, regardless of where the HVAC is installed (unconditioned or conditioned basement). If the system has a higher rating than the minimum efficiencies shown in the code, the building envelope will receive credit towards compliance.
If you do not have heating and cooling vents in the basement and therefore "render" the basement unconditioned, must you then insulate the ducts?
Yes, duct insulation would be required for ducts in unconditioned spaces. The minimum R-value of insulation on the ducts depends upon the location of your project based on heating degree days.
The following link offers additional information on this subject:
Does the Energy Code Allow an Unvented Crawlspace?
Does the residential pipe insulation requirement still apply when the pipes are on the inside of the conditioned building envelope?
For automatic circulating hot water systems, insulation is required regardless of installation location. Minimum pipe insulation thickness is dependent upon the service water heating temperature and pipe size. Other piping in the conditioned space typically does not require insulation.
When is the minimum SEER rating going to change?
The minimum SEER rating will change from a SEER 10 to SEER 13 in January 2006.
Is there an option for ducts located within conditioned space?
Ducts located within a conditioned space would not be required to be insulated. There is not an option to input or show ducts within a conditioned space in REScheck. The mandatory requirements for duct insulation, based upon location and the code, will be displayed in the Inspection Checklist.
There are other energy code requirements if ducts are located in conditioned spaces. Please refer to Details for Mechanically Vented Crawlspaces - Code Notes.