Achieving highly insulated buildings

Volume 18, Number 2

Canadian construction sector manufacturers, builders, and stakeholders are seeking to develop energy-efficient, cost-effective, durable and buildable solutions that are well-suited to Canadian construction practices. NRC’s response to these needs is part of a recently-announced initiative to develop and deploy new technologies for the benefit of Canadians and Canadian businesses.

Figure 1. The layers are put together with the VIP protected by Extruded Polystyrene Foam (XPS) layers. The top (external) XPS layer is 25mm thick, the bottom (internal) XPS layer is 20mm thick, the VIP layer in the middle is 15mm thick and is found inside a masking XPS layer.

Figure 2. A completed VIP module showing the tongue and groove method used for installation.

Figure 3. Two VIP modules are installed vertically through friction-fit tongue and groove.

NRC is partnering with government agencies and industry to explore, develop, test and document the energy performance, moisture response and durability of highly insulated residential wall systems. Measurement, simulation, and field trial results will be used to guide the development of durable new wall assemblies that exceed energy requirements in model codes.

Innovative use of traditional insulation

To achieve higher wall insulation levels in wall assemblies, it is commonplace to apply rigid, or semi-rigid, board insulation over the inside or outside of the framing. Alternatively, double-wall or deep-wall construction assemblies can be used to attain the desired thickness of insulation.

However, there are concerns that using progressively higher levels of insulation in wall assemblies to attain greater energy savings could result in moisture problems, given the impact that higher insulation levels have on the wetting and drying characteristics of the walls. The new research will help address the development of such unintended consequences, and will identify validated, de-risked solutions.

We welcome partnerships with industrial manufacturers or builders to ensure relevant products and designs have an opportunity for inclusion in the study.

VIP research

Research on significantly increasing the insulating value of retrofitted walls using vacuum insulation panels (VIPs) was recently completed by NRC in collaboration with industry clients. VIPs provide insulating values up to RSI 10.6 (R-60) per inch. The main obstacle to their use in buildings has been the risk of puncture damage during construction and the subsequent loss of insulating value.

Using NRC’s Field Exposure of Walls (FEWF) test facility, researchers tested two VIP configurations to study the impact of energy retrofit strategies on energy performance and durability. Both configurations had VIP panels sandwiched between rigid insulation boards. One used tongue-and-groove panels attached to the test wall by screws and the other used panels that were clipped to strapping. The tongue-and-groove arrangement was easier and faster to install but had slightly lower thermal performance compared to the clip-on method.

For both VIP walls, the additional insulation increased the internal temperatures of the assembly’s components, thereby reducing the risk of condensation in the walls. The addition of 55 mm of wall thickness added an insulating value of about RSI 8.5 (R-48), giving overall insulating values of about RSI 12 (R-68).

The hygrothermal tool hygIRC-C was used to determine the energy savings due to retrofitting the wood-frame wall systems with VIPs. It showed that the clip-on method had additional thermal resistance of R2, due to the effect of the air space between the insulation and the exterior cladding. The attachment methods and cladding used did not puncture the VIPs and the sandwich panel configurations facilitated changing a panel, should one be found to be faulty at the time of installation.

Building on successful initiatives in investigating VIP performance, we are currently seeking partnerships with clients and collaborators to participate in the development of cost-effective and robust assemblies that capitalize on the advantages of VIPs.

For more information

About these investigations, contact Wahid Maref at wahid.maref@nrc-cnrc.gc.ca or 613-993-5709.

About the hygIRC-C model, contact Hamed Saber at hamed.saber@nrc-cnrc.gc.ca or 613-993-9772.