What's a good and affordable insulation for concrete block walls?

[JVie]

I need your help on what good and affordable insulation will I use for my concrete block walls.

I want to DIY it myself and so I recon to install the insulations inside the room.

Thank you very much for your ideas.

[EricL]

Hello @JVie

Welcome to the Bunnings Workshop community. Thank you for joining us and sharing your question about insulation.

The ideal way to insulate your concrete block wall is to build a timber frame in front of it and install insulation into it. However, if you are after direct to block wall insulation I suggest using Foilboard 20 x 2400 x 1200mm Ultra 20 InsulationFoilboard 20 x 2400 x 1200mm Ultra 20 Insulation. Please make sure to use Sika 300ml White Sikaflex 11FC Plus Polyurethane Adhesive Sealant to attach it to your wall. 

Foilboard can be painted and mechanically fixed using recommended fixings. Please note that due to the soft nature of the Foilboard rough contact is not advised. 

Let me tag our experienced member @Adam_W for further advice.

If you need more information please let us know.

Eric

[JVie]

Thank you very much @EricL ..

Unfortunately, we don’t have Foilboard here in NZ, instead I may use EPS or expanded polystyrene board. Will it be good to stick it straight into the concrete block wall, will it not develop moist between concrete and the board that might develop into moulds overtime?

Again, thank you in advance for your help.

Cheers,

JVie

[EricL]

Hello @JVie

I'm sorry to hear there's no Foilboard in NZ. I totally agree with your thoughts on moisture and mold infestation. I suggest making a light timber frame to hold the EPS in place. I recommend using a spacer to create an air gap to prevent the EPS from touching the concrete block wall. You could also glue the EPS to the timber frame to prevent it from moving, please make sure to use the recommended adhesive for EPS.

Eric

[JVie]

Hi @EricL 

What is the recommended air gap in mm between the concrete wall and the EPS?

Do I need to make a gap between the EPS and the ceiling on the top, and gap with the floor as well for the air to flow? 

Again, thank you in advance for your help.

Cheers,

JVie

[EricL]

Hello @JVie

I suggest a gap of no smaller than 1/2 inch or 15mm. Depending on the size of timber you use a bigger gap of 3/4 inch or 20mm will also work. Leaving the same sized gap at the top and bottom is recommended to allow air to pass through.

Eric