ENERGY STAR’s New HVAC Design Report Eases Contractor Work
ENERGY STAR has become a strong, pervasive brand. It’s certainly an option for many appliances we see every day, and has become influential in consumer purchase decisions. What’s less commonly known, though, is that it’s also been building up a presence in the new housing market for over 20 years. The list of homebuilders who have ENERGY STAR houses is a long and impressive list of the best homebuilders. In fact, last year, there were 82,512 new houses able to obtain the coveted rating. Even more impressive, of the 190,180 houses which received a RESNET HERS Index in 2015, ENERGY STAR accounted for 44% of the ratings.
Up until now, the HVAC design reporting for ENERGY STAR was moderately clumsy and time consuming. There were substantial requirements for documentation, and several parts of the HVAC design information were spread around in multiple locations. To their credit, EPA staff has listened to feedback from the field, and recently released a new HVAC Design Report in Version 3, Revision 08, of ENERGY STAR, with much clearer requirements reduction in paperwork, and best of all, built into our software, Right-Suite Universal (RSU). As of March 9, 2016, it’s a free addition to current subscribers. In the future, it will be available from other software suppliers.
The new HVAC Design Report is built on top of ASHRAE 62.2 and ANSI / ACCA QI-2015 protocol, Manuals J, S, and D. It clarifies and simplifies five areas of HVAC: 1) Design temperature requirements, 2) Equipment sizing limits, 3) Group design policies, 4) Whole house ventilation, and 5) Duct design. Each of these has carefully thought-out ways to make the report easy to produce. Of course, once you’ve already done a system design in RSU, you only need to answer a few additional questions and press a button to print the report. Most of the information you need for the report is already in the design, so our integration eliminates double entry or hand filling in of the form.
Design Temperature Selection
Rev. 08 simply asks for the county of the house site, and then uses county weather data (based on Manual J or ASHRAE data) for every county in the US to set upper and lower limits for cooling and heating design temperatures. Rather than specifying the design temperature, Rev. 08 makes sure that you’re not exceeding the county limits, which keeps designs from overstating loads by design temperature stretching. While previous versions were subjective, this is a go-no-go decision.
The recommended approach for sizing limit is strict compliance with Manual S, but Rev. 08 also allows slightly higher tolerances in lieu of “next nominal size.” By combining Manual S definitions for heating or cooling dominated climate conditions with single-speed, two-speed and variable speed equipment types, clear and quantitative limits are provided as a go-no-go decision.
Production Home Group Design Policy
Ideally, every home built would have an HVAC system custom designed for it. In production home building, homes are frequently similar to each other, and the question comes up, do I have to re-design the HVAC system even though a new plan is very similar? ENERGY STAR criteria for using the same HVAC design for a group of homes is very pragmatic in five areas: If the HVAC design for members of a design group have 1) occupancy plus or minus 2 people, 2) maximum range of conditioned floor area of 300 square feet, 3) maximum range of window area of 60 square feet, 4) maximum range of predominant SHGC of 0.1, and 5) load variation across orientations of ½ ton, then the HVAC system design will be accepted by ENERGY STAR.
Whole House Ventilation
While previous versions of the HVAC Design Report only highlighted some of the design requirements for whole-house vent systems, now all design requirements are included in one convenient section. ASHRAE Standard 62.2 for both 2010 and 2013 are covered, and so there are inputs for ventilation airflow rate, cycle time, control location, whether the system is balanced, supply, or exhaust, and a number of other key control parameters. Efficiency and air inlet location are also included in one section of the report.
If you’ve done a Manual D design in RSU, then the duct section of the report will fill in automatically. Design system airflow, fan speed setting and static pressure are now in one neat spot in the report, and a single table lists rooms and airflows.
By working with main-stream HVAC design software vendors, ENERGY STAR has hit on a way to make the design process easily accessible for you. As more functions of HERS rating are built into the software you use every day, producing the required documentation becomes easier and easier. And there’s no denying that what’s learned and what’s put into practice to obtain an ENERGY STAR rating is following best practices. And contractors who grow by learning and pursuing new opportunities are the contractors who thrive.
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