In a past blog (“Return to Sender – HVAC Return Pathway Options”), a posted comment by GBAdvisor Mike Guertin introduced a new option for returning delivered air from rooms with closed doors, the Tamarack Technologies Perfect Balance. Perfect Balance is a grille and filter system installed into a cutout at the bottom of interior doors. Mike planned to install Perfect Balance in a number of rooms in one or more of his rentals and let us know what his tenants thought of them.

Guertin does some field testing

So, I checked in with Mike recently. “I have not heard anything back from my tenants; I guess no news is good news,” relates Mike. But Mike went one better: he tested door undercuts against Perfect Balance and reported on their performance in a Fine Homebuilding blog. The Tamarack Perfect Balance did a perfectly fine job of relieving pressure in rooms supplied but not returned with a forced-air system. In fact, Mike’s field testing came pretty darn close to the numbers cited on Tamarack’s website: 3 Pascals pressure difference while delivering 250 cubic feet per minute (cfm) of air flow.

This performance means that Perfect Balance meets either of the two Enterprise Green Communities Single Family Rehab Specs for pressure relief (6339 or 6340).

Nelson Warner, VP of Research and Development at Tamarack, says that if the room is large and has too much supply air delivered for just one Perfect Balance to provide the required pressure relief, some users have added a second Perfect Balance at the top of the door, even adding some convective (high-low, warm-cool) air transfer to the room.

Light and sound transmission

I asked Nelson Warner if he had any results from third-party standardized testing of sound transmission on Perfect Balance.

“No, we don’t have that type of test information,” he reported. “But I can tell you two key results from field testing we have conducted. One, the fit of the door and particularly the type of flooring surface on both sides of the door has the most impact on sound transmission. And two, when we measure sound transmission before and after installation of Perfect Balance, we get essentially the same results.” In other words, Perfect Balance will not improve the sound performance of the door, but it won’t erode its performance either.

And because Perfect Balance has a filter insert between the two surface grilles, light transmission is not significantly different before and after installation of Perfect Balance.

What about cost and availability?

The Perfect Balance grille is simple to install and comes with a lifetime guarantee. At $29 (plus shipping) , Perfect Balance is surely cost competitive with the alternatives for new construction and far cheaper than any alternative (except a 1.5+ inch door undercut, an approach that comes with big-time privacy and aesthetic issues) for retrofit.

Tamarack Technologies is a relatively small but innovative company in Massachusetts; since their products are all made in the U.S., they ship the same day the order comes in. Tamarack currently works with several builders who order hundreds of Perfect Balance kits at a time, with Tamarack shipping their Perfect Balance kits to the manufacturer of the builder’s interior doors. That way the Perfect Balance units are installed at the door manufacturer’s facility and the doors are ready to go at the job site.