Insulating an External Wall

[Willmott85]

Morning all.

Firstly I hope this is the correct section to post in. Seemed the most appropriate, but if not, please feel free to move, or advise where I can move it to.

I am in the process of renovating an 1930's property, which comes with lots of quirks. I would like to add some insulation to the wall around the front door, but have a few questions about how best to do this.

Some Background

When the house was originally built, it had an external porch in front of the front door, with a lovely arch as the opening. The front door, and wall, was set back from this arch approx 1.5m. At somestage in the properties history, a past owner has removed the old front door/wall, and moved the front door to within the archway. The exposed brick of the old external porch was simply boarded over with. This boarding has been removed now, and you can see in the pictures below the current state (and also how the old wall position used to be).

We are having a new front door fitted (old one still shown), along with renovating the whole house. As nice as the old imperial brick is to look at, it is not great for heat retention. So I would like to add some insulation to this 'front' wall internally, either side and above of the door.

The Questions

1) My original plan was to create a stud frame on the brickwork, and infill with 50mm PIR board. This could then be plasterboarded over ready for plastering.

I am now wondering whether it is best to just add insulated plasterboard to the wall instead?

2) With the above in mind, do I need to apply a breather membrane under the stud wall/PIR or insulated plasterboard? If yes, any recommendations on what product to use here?

For reference, most walls have been cavity filled with bead by a previous owner. I am unsure on this small section of wall. It is cavity for most of it, but as you can see from the second picture, the external detailing (which is lovely) reduces to single brick depth at the very edge of the arch.

3) If yes to the breather membrane, how should it overlap, or not, onto the ceiling (already plasterboarded) and floor (concrete)

Thanks in advance for any help you may be able to provide.

 

[^woody^]

A foil backed insulation between and over battens is the most efficient. However for such a small area and to save a lot of messing about you may as well just use an insulated plasterboard on dabs.

No membrane for either

 

[Dereekoo]

you may as well just use an insulated plasterboard on dabs.

Not if its solid brick construction?

 

[^woody^]

Not if its solid brick construction?

Why not? It's the same as plastering a solid wall.

 

[Dereekoo]

Why not? It's the same as plastering a solid wall.

Thats a very good point Woody and I would suggest its to do with the dab being susceptible to degradation from moisture permeating from the outside and is a similar thing to lining the back of any battens used if going down that route with DPM to stop moisture affecting the timber.

Kingspan advises the folllowing

Drywall Adhesive Dab Bonding  Drywall adhesive dab bonding must always be used in conjunction with a bonding agent applied to the foil facer, as per the following sitework instructions.  This method is suitable for use on brick, block or concrete cavity or rendered solid walls, which are dry, stable and free from moisture penetration.  This method is not suitable for use directly on nonrendered solid masonry walls where there is a risk of moisture penetration, or on timber or steel frame construction.

I guess it all hangs on the perceived risk of moisture penetration, yer pays yer money and yer takes yer chance as those funny Yorkshire folk say.

 

[Willmott85]

Thanks for the replies.

A foil backed insulation between and over battens is the most efficient. However for such a small area and to save a lot of messing about you may as well just use an insulated plasterboard on dabs.

No membrane for either

I don't mind doing this. Especially as the better option for heat retention.

Just to be clear then, your proposing batens down first on the wall (to create a small cavity to the back of the PIR), then the foil faced insulation, then the plasterboard on top?

I have done some further reading and many suggest a membrane between the wall and the batterns. Any preference on the type of membrane for this?

 

[^woody^]

No cavity, no membrane.

50x25 battens, 25mm PIR between, 25mm over the face.

 

[^woody^]

Thats a very good point Woody and I would suggest its to do with the dab being susceptible to degradation from moisture permeating from the outside and is a similar thing to lining the back of any battens used if going down that route with DPM to stop moisture affecting the timber.

Kingspan advises the folllowing

Drywall Adhesive Dab Bonding  Drywall adhesive dab bonding must always be used in conjunction with a bonding agent applied to the foil facer, as per the following sitework instructions.  This method is suitable for use on brick, block or concrete cavity or rendered solid walls, which are dry, stable and free from moisture penetration.  This method is not suitable for use directly on nonrendered solid masonry walls where there is a risk of moisture penetration, or on timber or steel frame construction.

I guess it all hangs on the perceived risk of moisture penetration, yer pays yer money and yer takes yer chance as those funny Yorkshire folk say.

Board adhesive sticks better than bonding or browning, so it wont be a problem on a solid wall.

But that's a cavity wall anyway in the OP

 

[Willmott85]

No cavity, no membrane.

50x25 battens, 25mm PIR between, 25mm over the face.

So, as per below?

Out of interest why do you suggest no membrane, or cavity? Not questioning your opinion, just wanting to learn

Given the wall goes to solid at the very edge of the arch, would this be an issue?

 

[^woody^]

Voids and cold surfaces in a wall construction create a risk of interstitial condensation.

You don't need a membrane because you just don't have a need to prevent damp.

 

[CACKATALLTRADES]

Is there really any point? Seems like a lot of effort for a negligible improvement in energy efficiency given the proportion of the wall occupied by the door. You've got all your coats hanging up there looking untidy anyway so why not just reinstate the porch?

 

[Willmott85]

Voids and cold surfaces in a wall construction create a risk of interstitial condensation.

You don't need a membrane because you just don't have a need to prevent damp.

Because of the precense of the cavity, regardless of size or insulation within?

Is there really any point? Seems like a lot of effort for a negligible improvement in energy efficiency given the proportion of the wall occupied by the door. You've got all your coats hanging up there looking untidy anyway so why not just reinstate the porch?

Thanks for your helpfull input to the discussion. Firstly, as per the original post, the door is still to be replaced, which itself is more thermally efficient than the existing. Secondly, it's hardly much effort to add in some insulation given we want to plasterboard and paint (to cover over the brick wall) and lastly, the coats hanging there are a temporary solution while we complete the works. But thanks for your concern of them "looking untidy".

 

[mcprinter]

DIYer in a 1930s House.
Nothing constructive to add but love the External Brickwork around the Door.
Glad to see you are replacing the Door.
Didn't notice the Coats