Build Smarter: Where to Use SIPs in Your Home

Energy efficiency is often the highest priority for people building with Structural Insulated Panels (SIPs) , but sometimes other priorities need to be managed to achieve the outcomes that clients want. Sometimes, people think a house is either high-performance or not. But in reality, there are many levels of performance, and by making some small changes, you can drastically enhance the performance of your home without being too expensive or altering your design. This article will go through how using SIPs for different components of your build can help you achieve your different project  requirements.

Formance can supply SIPs for floor, walls and roof. Some projects go with all three. Whilst walls and roof are the common combination, using one component (i.e. just walls) can be a good way to achieve higher performance than standard, whilst being a more cost effective option.

It can be broken  down into three packages that are easy to understand and communicate with your clients. Although simplistic, the diagram below shows these different options and is a good visual guide for decision-making. 

Other things might change between these different packages too. Things like graphite infused EPS, windows, and ventilation are all factors that will also influence home performance.

On projects where the budget is not sufficient for a full SIP envelope, using it for just the walls is the best way to increase performance whilst remaining affordable. Thermal modelling shows that a typical house will be 30% more energy efficient by changing just the timber framed walls to SIP. It also addresses a key concern that a lot of people have about typical fibrous insulation; slumping over time. Using SIPs in your walls means there willl be no slumping, always highly insulated, low in thermal bridging and high in airtightness.

Using SIPs for the roof only  is also a viable option but typically isn’t as cost-effective as the walls only option. This depends on the specific roof design and the spans as sometimes SIPs can be more cost-effective, especially when it comes to vaulted ceilings and skillion roof designs, etc. Using SIP walls and roof greatly enhances the performance of the home and typically makes it a minimum of 50% more energy efficient than a home built to the NZ building code. As the airtightness layer is continuous, it also means that the home will do better for air retention and score well in blower door tests. Most Formance homes go with this option, as it's a trusted way of achieving high performance. Often passive homes are constructed using this “package”, due to the continuous airtightness and other thermal efficiency.

Going with the “best” package is when you’re aiming for the passive house level of performance, and the houses we’ve modeled using this recipe are often below the 15kw/h mark, meaning they are passive without much consideration for specific design and site conditions. However, this option is understandably the most expensive, which means that we only do a few projects at this scale.

To get an accurate answer on performance, we’d always recommend undertaking thermal modelling to value engineer the design to achieve the project priorities. Formance offers this service and can work with your client directly with different product selections in order to achieve their goals.

In summary, using SIPs is a great way of increasing your home’s performance and reducing power usage, and how you don’t have to go the “whole hog” for every home, acknowledging other priorities on a project. 

The best way to find out which option will work best for you or your client’s project is to talk directly with Formance for no-obligation advice. 

Ring us on 0800 000 527 or email [email protected] to get in touch.