Adding insulation to attic rafters

peustace

Hi, would appreciate if anyone can give me some guidance on this. On the top floor of our house we have 2 rooms and attaic space at the front and back.

I've added an extra 200mm of insulation on top of existing 200mm insulation in the space of the attic which I think should be sufficient but open to other opinions.

Now I'm trying to determine what next I can do, and I'm thinking that more insulation could be put in between the rafters above the top floor rooms (See photo 1 and 2 attached). At the moment there is only about 1cm of airflex insulation.

There is also about 1cm of airflex on the vertical stud partitions of the top floor rooms (see photo 3).

Shoud I increase insulation in both these spaces, and if I could what would people recommend on the best material?

Appreciate the help!

dathi

http://www.siginsulation.ie/wp-content/uploads/2012/07/KDB_Airflex.pdf
even their own literature says that airflex is not enough insulation on its own

Calahonda52

OP can you reference your project using the following attachment so as we know what is what.

If foto 1 is at the intersection of 1 & 2 in my attachment then the cold air can get behind the aeroflex.

The foil if done properly is airtight, not breathable, to the room.
The roofing felt looks as if it is breathable

https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx may help

As may this
https://www.linkedin.com/pulse/maximizing-energy-efficiency-roof-niall-crosson

strip out the branding and focus on the methodology and material properties, bearing in mind that the all foil stuff, if properly taped is airtight, not breathable,

peustace

This has taken me a long time to get back to this. I eventually got around to drawing out an idea of what the attic looks like

peustace

Here's the drawing attached

Calahonda52

Okay,thanks for the sketch.
Do you know for the airflow is there an air gap between it and the plasterboard on the knee wall and sloping roof.?

NIMAN

OP,

I have similar spaces in my house, and had thought of adding something like this between the rafters
http://www.wickes.co.uk/Wickes-60mm-Polystyrene-Rafter-Insulation-Board-0-74-M2-Pack-3/p/210020
That was after getting a huge quote of €3200 to have the rafters done with sprayfoam, which I couldn't justify.

Then I have also read that there is little point of insulating between the rafters, as the crawl space is meant to be ventilated and will always be cooler than the rest of the house.
It would be more important to insulate the walls between the crawl space and the internal bedrooms (ie the vertical walls) in your sketched the vertical wall with the 4 little scribbles on it.

Calahonda52

NIMAN wrote: »

OP,

...Then I have also read that there is little point of insulating between the rafters, as the crawl space is meant to be ventilated and will always be cooler than the rest of the house.

In general I would agree but there are cases where it is done.

It would be more important to insulate the walls between the crawl space and the internal bedrooms (ie the vertical walls) in your sketched the vertical wall with the 4 little scribbles on it.

This is what we need to know the construction of, the knee wall: it looks like it could be a dog to do correctly all the way along.

NIMAN

My knee wall (didn't know they were called that until now!) is crudely insulated with some rockwool.

Is that the normal practice?

Is there a better option?

Would putting spray foam on the knee wall be a cheaper option to spraying under rafters?

peustace

So I just have airflex material on the knee wall (hey I learned a new phrase! ) so I guess I could look to improving the insulation in this location. Still not sure about under the floor and then above the ceiling between the rafters whether it would be worth doing anything

Calahonda52 - I'm not sure about the airflow. Is there a way I could check, what would I be looking for?

Calahonda52

peustace wrote: »

So I just have airflex material on the knee wall (hey I learned a new phrase! ) so I guess I could look to improving the insulation in this location. Still not sure about under the floor and then above the ceiling between the rafters whether it would be worth doing anything

Calahonda52 - I'm not sure about the airflow. Is there a way I could check, what would I be looking for?

My apologies I meant airflex , not air flow.
What I am asking is there an airspace between the airflex and the plaster board?