Fitting Rigid Insulation Under Siding

The vinyl and fibre board siding strips popular in Calgary have not kept pace with warmer and cooler seasons. They can no longer cope with cold winters on their own, and as a result we are beginning to turn the HVAC higher.

This means we consume more energy, and this increases our carbon footprint further. Fitting rigid insulation under siding tackles both problems simultaneously, so it’s a good thing to do. It should also pay for itself over time through lower energy bills.

More Benefits from Fitting Rigid Insulation Under Siding


Rigid siding impedes the transfer of ambient winter cold, and summer heat into our homes. Vinyl and fibre siding can’t do this entirely on their own, even with every joint sealed tightly. The dew point, at which atmospheric droplets begin to form moisture could still enter the wall cavity, and condense there.

Damp could also directly enter the wall cavity in the form of wind-blown rainwater and sleet. The force of the wind, and the power of capillary action can work this through the tiniest gap. Fitting rigid insulation under siding adds a second moisture barrier to building wrap, and helps protect the sheathing and framing further.


But the main advantage of rigid insulation is it improves the thermal performance of the building. That’s why architects are retrofitting it over large brick and mortar buildings as we show in the image below.

Firstly, it improves the ‘R Value’ of the structure by strengthening its ability to prevent temperature transfer. But that’s not all. Rigid insulation also reduces the amount of air entering your home from outside. This contributes to the warmer, less humid air you imagined when you purchased your home.

When the Best Time to Install Rigid Insulation Under Siding?

It makes sense to do this when you change the siding on your home, because of labour savings. However, we could also do the job in phases, wall by wall and could have the rigid insulation in place the same day. If not, then summertime could be your better option.

Speak to Valiant Exteriors on (403)829-1661 in Calgary,or post them a note on their website if you would like free advice. We are your friendly local specialists. We live in Calgary, we understand because we share the same climate with you.

fitting rigid insulation under siding
Installing Rigid Insulation on a Building Exterior (Image Cjp4 BY CC 4.0)



Insulated Vinyl Siding Is It Really Worth It?

Informal Style with Board and Batten Siding

Detail Image of an Insulation Board (Credit Cjp4 BY CC 4.0)