The Pros and Cons of Building with SIPs

SIPs are a modern construction technique that involves sandwiching rigid panels made of foam or polystyrene insulation between Oriented Strand Board (OSB).

These prefabricated boards can then be simply slotted together to create the structure of the building, and the method is commonly used in the residential and commercial sectors.

Like any traditional or modern building method, structural insulated panels come with a number of advantages and disadvantages.

Energy Efficiency

The main benefit of building with structural insulated panels is that they are super energy efficient. This energy efficiency is achieved in a number of different ways, the first one being that the material is a great thermal insulator. 

With the panel's insulating foam core, it allows homes to retain heat when it’s cold, and keep hot air out during warmer spells. This effect is enhanced by the airtight construction. By minimising the leakage of air, this building method is able to better regulate the indoor temperature.

Because of this airtightness, SIPs require a unique ventilation system known as mechanical ventilation with heat recovery (MVHR). Unlike traditional ventilation systems, they allow air to circulate in and out without losing heat. Again, this helps to make the building extremely energy efficient.

Structural Integrity

When looking at these panels on their own, you may mistakenly believe they are weaker than traditional methods such as a timber frame. However, they are actually 7 times stronger than a timber frame structure, due to the monolithic shell that the panels form once complete.

This gives the building great structural strength and allows the structure to withstand extreme climates and harsh weather conditions.

The actual building process with SIPs is much more straightforward than with traditional methods, as the panels are manufactured offsite. This means less waste, less time spent on site and minimal construction errors, since the panels are precision engineered. 

There are also additional benefits to manufacturing offsite, like if the site has difficult access. Minimising the equipment and materials required on site can make the process much more straightforward.

As well as being easier, constructing with structural insulated panels is also generally much quicker too. This is because the panels come pre-cut and ready to put together, whereas on a traditional site, time would need to be spent preparing the materials and waiting for deliveries.

SIPs can also be constructed in any weather conditions. The weather is famous for halting building projects in their tracks, but when choosing this modern method of construction, the project timeline should run smoothly and to schedule.

Structural insulated panels have a number of green credentials which make them a much more eco-friendly option than other methods. Because they are so energy efficient, the energy consumption (and therefore the operational carbon) of these buildings is kept to a minimum.

While SIPs still require timber, they use a whole lot less of it than a traditional timber frame. Also, the exterior of the panels is made from oriented strand board, which is a material made from fast-growing trees. Because of the fast regeneration rate of these trees, the environmental impact of cutting them down for materials is kept to a minimum.

While building with structural insulated panels offers a number of benefits, no method is perfect. There are a few disadvantages to be aware of when constructing with SIPs.

SIPs have great insulation, but the airtightness of them doesn’t allow for great ventilation unfortunately. It’s important to address this problem during the construction process as poor ventilation can have a knock-on effect, leading to accumulation of pollutants, poor air quality, increased humidity and fire hazards.

Investing in a mechanical ventilator (an MVHR system) should keep these problems at bay, hence why most SIP projects opt for this kind of ventilation system.

One main downside to building with structural insulated panels is that the materials (such as the wood) are prone to water damage, such as rot, mould or mildew.

Installing a waterproof surface on the walls can mitigate this issue, as can installing heat ventilators in humid areas (such as bathrooms and kitchens).

The precision engineering of SIPs are great for a number of reasons (especially during the construction process) but unfortunately, this process means they don’t really allow for changes in the future.

Even smaller renovations like adding plumbing or electrical lines is difficult once the building has been constructed as all of the holes for these systems come pre-drilled.

These limitations mean that you really would need to get the building right the first time, or face a costly price to change it later. But as we know, the needs of a building normally change over time so SIPs don’t really lend themselves to that.

Cost is an important factor when it comes to constructing, especially on large-scale developments where a per-unit cost increase could massively push up the price of the overall scheme.

While structural insulated panels are ultimately cheaper in the long run (due to reduced energy bills and running costs), constructing with the panels is more expensive (by approximately 10%) than construction with a wooden frame.

They may require a slightly larger upfront budget, but in the long run the benefits are sure to make this initial investment worth it.