Tuesday, January 31, 2017: 11:00 AM-12:00 PM
Building Operation and Performance
Chair:
R. Christopher Mathis, Mathis Consulting Company
Sponsor: Residential Building Committee
The late, great Yogi Berra once said: "In theory, there's no difference between theory and practice. But in practice... there is." The speakers at this seminar agree with Yogi. Using measured data from both dry and humid climates, they show how actual energy and thermal comfort in real-world houses differs from expectations. But beyond the problems, the speakers also show data from specific designs and installation practices that have helped contractors meet and exceed customer expectations with simple, low-cost, reliable equipment instead of whiz-bang, expensive stuff that too often fails to deliver comfort and low energy performance.
1 How Dry I’m Not: Measured Humidity Loads vs. Measured Dehumidification By Heat Pumps in Occupied Houses
High humidity can be a problem. It’s uncomfortable and it’s a mold risk factor. ASHRAE and ACCA load calculation procedures provide equations to estimate dehumidification loads in residential buildings. But sometimes, it’s instructive to measure the loads in real, occupied houses, rather than just estimating them. The same goes for dehumidification performance of AC units. Measurements from occupied houses and apartments in Europe and the US suggest that both ASHRAE and ACCA load calculations greatly underestimate actual residential dehumidification loads.
2 What Works and What Does Not: Measured Residential HVAC Performance and Comfort in Dry Climates
Performance contractors sometimes say: "In God we trust... all others bring data". Shasta, California has a climate with sensible cooling and heating degree-days similar to those of Chicago. But in our dry climate, we can heat a three-bedroom, 2,400 ft2 house with less heat than a hair dryer, and cool it using one (1) ton per 1,200 ft sq. The data shows comfortable temperatures by using low-cost, constant-volume, low-SEER cooling equipment. The secret is relevant in-process installation measurements, combined with the unusual practice of actually following design guidelines known for decades to be best practices.