Page 28 - Green Builder Sept-Oct 2016

best option out of the many available on the Required whole-house supplemental dehumidification capacity based on different
market today. It also will make layouts more DP design conditions for three new construction house efficiency levels.
consistent and provide easier field inspection.

Though the product is still a few years
away from being available on the market, it’s
been well received by the building industry
in IBACOS’s test runs. IBACOS is currently
demonstrating the technology and working
on partnering with a manufacturer to produce
the product.

“In early 90s, we were looking at how to
distribute air in a room more effectively. This
is the next evolution,” Grisolia says. “The time
for this is now, because energy codes push
builders to build more efficiently—which
makes this product a more viable solution.”

DEHUMIDIFICATION

Before the era of high-efficiency homes, air CREDIT: NREL

conditioning was usually sufficient to remove

moisture. However, tighter high-performance

building envelopes lead to less peak and New systems. Accurately calculating the amount of dehumidification needed can be
seasonally sensible cooling loads. This leads to reduced by better measuring humidity levels.

smaller air conditioners, shorter peak cooling

seasons and lower system airflow rates, A typical building load profile (a) based on outdoor DB temperature and (b) estimated air
according to the DOE’s Market-to-Research conditioner RTF for a typical new construction home in Houston, Texas.
Plan.

“Better walls and windows do a lot toward

reducing sensible load,” says Jon Winkler,

senior engineer for the National Renewable

Energy Laboratory (NREL). “But we still have

ventilation air and occupants, so latent load

is becoming a larger portion of total load.”

However, the plan states latent loads are

not reduced as much as sensible loads due

to internal gains and fresh air ventilation.

Sensible cooling load is influence by factors

such as doors, windows, attics and roofs.

Latent cooling load is influenced by people,

appliances and air seeping in through the

building envelope.

These factors make humidity control CREDIT: NREL

much more important. As a result, NREL

is working to develop an affordable, better

dehumidification system that would provide Accurate measurements. Measuring outdoor dry bulb temperature can help a builder
dehumidification all year. The system would determine the amount of air conditioning needed.

tweak Manual J calculations—the industry standard for determining the humidity load of a humid day, according to Winkler.

how much heating or cooling a home needs—to determine optimal To validate the new theory, NREL compared its modified

conditions to avoid moisture year round. Manual J calculations to Energy Plus simulation results. It used

Currently, Manual J uses 1 percent dry bulb temperature to an HVAC system designed for a home using the modified Manual

measure the climate temperature for the AC unit. But according J calculation and put it in a simulation with Energy Plus. That way,

to NREL, only 1 percent of all hours in an average year are hotter NREL could study the results in various climates without owner

than that temperature; 80 hours per year are not. Instead, NREL is interference.

looking into changing the assumption in a Manual J calculation to a The improved calculation can help homeowners save upfront costs

2 percent dew point instead. That measurement can better estimate by determining how much dehumidification is actually needed.

26 GREEN BUILDER September/October 2016 www.greenbuildermedia.com