Thermal Bridging: More than Just Saving Energy

Recently Andrea Love and I presented PAYETTE’s thermal bridging research at the Healthcare Facilities Design Conference. We challenged ourselves to make this topic relevant for a design sector that has not begun to broadly address it in their work. Why not, you may ask? Well, most architects (and owners) in healthcare view the internal design loads of their buildings as the driving factor, marginalizing the gains that exterior envelope performance has on a energy use. We disagree with that approach for several important reasons.

Energy savings, no matter how small, are savings. Currently, all-air HVAC systems predominate in healthcare facilities. With this strategy massive amounts of “once-though” air are conditioned to 55 degrees, compensating for small percentages of peak internal loads and uncontrolled solar exposures. However, the majority of building air is reheated back up to room temperature to provide comfortable interiors. There is a high operational cost for this inefficiency. Similarly, these buildings’ exterior envelopes are often designed to code minimum and exterior heat loss is treated as a secondary or tertiary factor in overall building performance.

First, we put the situation into perspective. Our research proves that thermal bridging in all types of facades, whether from detailing or material selection, reduces performance by 40% to 80%. No matter what the internal loads, this creates a tremendous burden on utility consumption. Simple improvements in detailing and construction methods will save energy.

Next we reflected on the particular context of healthcare: sick patients, fatigued family and overworked caregivers. These buildings house people at their weakest and most fragile moments of life and the comfortable environment we create is much more important that in the average commercial building. From this perspective, improving a window or wall detail means more than just reducing heat loss. I believe it means that a parent will sleep comfortably through the night on a sofa next to the window in their child’s hospital room; that a cancer patient enjoys the view to a garden during their infusion treatment without feeling cold and exposed; that a care-giver in scrubs relaxes comfortably in a lounge without turning on space heaters or donning winter coats.

Another hidden benefit of controlling thermal bridging is the prevention of mold growth in the wall cavity. While continuous air barriers provide a first line of defense, eliminating condensation risk at the dew point is critical. This is especially true in humidified healthcare facilities where static pressure and exfiltration (the opposite of infiltration) constantly drive warm, moist air into wall cavities during winter months.

From our audience’s response, it was clear that our presentation made a difference. We felt confident that these healthcare design professionals and facility managers left with an increased awareness of the importance of good facade design – and that thermal bridging and thermal comfort often go hand in hand.