Improving the U value of a hardwood door

[Adsibob]

The side door to our house is a solid hardwood timber door. Probably about 2m in height and 85cm in width and about 52mm thick. Not sure of the wood, but definitely a solid hardwood door, very dense. Google tells me the U value of a hardwood door is about 3W/m²K.  Due to budgetary constraints we weren't going to replace this as part of our refurb, but I'm now starting to wonder if this is a weakness in our thermal envelope. The door is in a solid double brick wall to which we are adding 40mm of EWI (phenolic boards) plus about 6mm of render, so it will probably have a U value of about 0.54 W/m²k.

 

The obvious answer is to replace the wooden door with something with a much better U Value. But I want something budget. Could I add insulation to the door? Maybe some of the 40mm phenolic boards, then a plyboard frame and then paint it? 

[Adsibob]

Would doing something like the 7 steps at the end of this work:

 

https://www.wcmanet.org/how-to-build-an-insulated-exterior-door/

[Cpd]

 May not work for you but I have added kingspan to  many of the doors on my property, I put 50mm on some doors  but usually just add 25mm and then put a sheet of ply over it, if I am being fancy I put edging strips on to hide the kingspan but mostly I just seal the edges with tape. The door in the photo is to my heated shower room in my cabin, it’s got 27mm if larch on the outside, 50mm of kingspan and 10mm ply on the inside with edging. It’s all very rustic and not for everyone but I like knowing I am not loosing loads of heat from this room. 

[Ferdinand]

On 17/10/2021 at 20:08, Adsibob said:

The side door to our house is a solid hardwood timber door. Probably about 2m in height and 85cm in width and about 52mm thick. Not sure of the wood, but definitely a solid hardwood door, very dense. Google tells me the U value of a hardwood door is about 3W/m²K.  Due to budgetary constraints we weren't going to replace this as part of our refurb, but I'm now starting to wonder if this is a weakness in our thermal envelope. The door is in a solid double brick wall to which we are adding 40mm of EWI (phenolic boards) plus about 6mm of render, so it will probably have a U value of about 0.54 W/m²k.

 

The obvious answer is to replace the wooden door with something with a much better U Value. But I want something budget. Could I add insulation to the door? Maybe some of the 40mm phenolic boards, then a plyboard frame and then paint it? 

 

Can you add a budget door opening the other way the other side of the wall?

[JohnMo]

Our door has 15mm PIR insulation within it and it gets a U value of 1.0.

 

You could do the same on the internal face and then over clad with some ply and paint.