UK households may have seen some respite from the excessive gas and electricity prices of recent years, but these still average £100 per month for each and are a substantial chunk out of paychecks. Gas heating is relatively efficient, but newer sources like heat pumps are steadily being implemented to reduce costs further. With that said, the generally low level of insulation, especially in older homes, causes most financial headaches.

If you’re feeling the cold and still dipping into your account for the privilege, consider assessing how much heating your home loses. Roofs account for a third of lost energy, walls about half, and floors roughly a fifth. The best and most cost-effective way to keep heat in and provide a cosier home is to use PIR insulation boards. These come in varying thicknesses, so they fit areas in older buildings and new developments, and they are widely available from half a dozen brands. Boards of medium thickness, such as PIR insulation board 75mm, are general-purpose products used in slanted and flat roofs, ceilings, framed and cavity walls, and concrete and suspended timber floors.

What Is PIR Insulation?

PIR, or polyisocyanurate, is a thermoset polymer made of isocyanates and polyols. The substances bond when heated in the presence of a blowing agent and additives, creating a closed-cell rigid foam. The foam is shaped into boards in standard building sizes and is lined with facer and backer foils to improve the already high fire and moisture resistance. Where PIR boards excel, though, is their excellent thermal properties, effectively resisting heat transfer in areas where they are installed.

Properties, Benefits and How It Compares to Other Insulation Materials

Compared to similar insulation products, like polyurethane (PUR), expanded (EPS) or extruded polystyrene (XPS), PIR has more going for it, despite costing not much more. First are the very high R-values, or thermal efficiency. PIR boards are up to 15 percent better at keeping warmth in than their PUR cousins in the same thickness, and almost twice as good as comparable EPS and XPS boards. This means boards of moderate sizes, like a 75mm PIR insulation board, will retain the same amount of heat inside a room or building as an 80mm PUR board, a 110mm XPS board, and a 140mm EPS one. PIR boards make more sense if you need high thermal performance but have limited space (such as on floors).

Another plus is that thinner boards of any type are cheaper, so you’ll be saving on two accounts. But besides cost, PIR insulation trumps other insulative products in other critical areas. Boards are much denser, offer structural rigidity to bonding elements, have very high impact resistance, and keep their form under high loads. This makes them ideal in areas like floors with high foot traffic as well as roofing applications. The boards can function on their own or are combined with insulated plasterboard for even higher durability.

To meet strict fire standards in new builds, PIR insulation beats competing boards. It may not have the fire resistance of mineral or glass wool, but it won’t catch fire, melt or spread fumes. Crucial here is to consider the isocyanurate index, as different PIR boards are rated differently. On the whole, though, all perform better in fires than PUR boards and much better than combustible options like EPS.

How well the boards hold up to moisture and humidity also increases their versatility. Here, the aluminium facer materials act as barriers that wick away water and liquids, making this the ideal roofing solution. They also prevent moisture and mould buildup in interiors.

Lastly, polyisocyanurate is an eco-friendly insulation material. It is recyclable, uses little energy to produce, and can be repurposed for other uses. Since it is a closed-cell structure, it has no fibres that can potentially cause respiratory issues, like insulation wool and fibreglass. In addition, it doesn’t deform or rot over time and is rated to last for the lifetime of the building.

Where Are PIR Boards Used?

Favourable properties, low cost and very low weight make boards easy to transport and install. Boards of different thicknesses are preferred for different insulation purposes, largely due to space restrictions. Thinner PIR boards, those in 25 and 40mm, are used in framed walls, floors and pitched roofs. 50 and 75-mm PIR insulation are common in solid and cavity walls, as well as roofing projects, including flat roofs. And 90, 110 and 150mm variants are more common in external wall insulation and roofs, often bonded to plasterboard.

Thickness determines the overall thermal efficiency. Understandably, the thicker the board, the more warmth it retains. Price differences between boards of one thickness and the next, for instance, between 50 and 75mm, are quite acceptable, so where there’s enough space, opt for thicker insulation if you’re after more warmth and lower bills.

Buying and Installation

There are a few considerations when purchasing and installing PIR insulation boards. First, consider the scope of the project and whether you’ll require the appropriate approval or permit. The next basic measurements of the planned area or room will give you a rough figure of how many boards you need. Polysio boards are sold in standard building sizes of 1200 by 2400mm, either separately or in packs of 4 or more. As mentioned, there are a few British brands to choose from, and PIR boards are marketed for different uses.

Installing PIR boards is done per manufacturer recommendations. This can be done using the dot-and-dab method, using a bonding agent on both boards and walls and adhesive tape in jointed boards and along edges to prevent thermal bridging. Fasteners can also be used to secure the boards to structural elements and ensure they stay in place during fires or other occurrences.

Boards are also joined using metal fixings, aligned at the edges. Of course, before installation, you’ll have to measure each board and cut it to size. This can be done with any saw or utility knife. Walls, ceilings and roofs also need to be free of dust, debris, paint or wallpaper to ensure that boards stay put once the bonding agent has cured.

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