Third layer of attic insulation?

hoodie6029

Hi folks,

Rolled out two layers of insulation in the attic recently. The two bigger bedrooms are still a bit chilly compared to the smaller bedrooms since I’ve done it.

I have some rolls left over. Is there any harm in adding a third layer over these rooms? Or is there a chance that this would compress the layer underneath?

Thanks in advance.

10-10-20

Hi.

Maybe define what the problem is here a bit better - "chilly rooms" isn't very clear as it doesn't tell us about when they are chilly, or what your heating method and duration is or whether the rooms are retaining heat but just for sufficient duration. For example: My bedrooms are "chilly" in the daytime hours between 08:30 to about 9 at night as they aren't heated as they aren't used - but they are insulated with ~200mm of insulation!

What temperatures are the rooms hitting when chilly and how is your hour constructed and what other insulation is in the walls, etc... Were air-leaks into the attic addressed before the insulation was previously topped-up?

Layering insulation is likely to compact the insulation below, but I believe that the effect is not overly significant. But I'd suggest that it might not provide the benefits which you are looking for as it's not addressing the chillyness holistically.

loyatemu

I'm not an expert but I've read similar threads where people have said there's very little marginal gain to be had from rolling out a third layer in the attic. If the rooms are still cold it's for different reasons. I know in my house the 2 bedrooms on the gable end of the house are colder because the gable wall is like a big anti-radiator.

Sleeper12

Back of my house is always warm. South facing. Front rooms are always cooler. 300mm attic insulation but several degrees of a difference between front and back bedrooms. There is no amount of attic insulation in the attic will change this fact

As pointed out above, too much insulation can compact and reduces the quality

TimHorton

https://www.boards.ie/discussion/comment/120002815#Comment_120002815

I have the same problem with 2 Bedrooms on the North End of my Bungalow - 1st job was to remove existing 18 yr old Attic Insulation and replace it with 300 MM of new Insulation. This made an instant improvement , I have just completed adding 100 MM Rigid Polyiso Insulation to the inside of the external walls. This required the moving of a radiator and extending 2 x sockets. Still not complete but even in -4c weather the room is warm getting up to 20c after 45 mins using a small fan heater. I also removed the window board and sealed all around Window - I also added 25mm Insulation around the 4 Window reveals. Used AirTight Tape/Membrane around pipes/sockets/Window Reveals. The 2 external walls are 100% Covered in Insulation. Next phase is to add a Vapour Control Layer then 2x2 Battens followed by 12.5 foil backed Plasterboard. The cost of Materials (1 room) is about €800 so far. Once complete I will assess and then move on to next room early in the new year if all goes well. It has taken a while but I have learned lots , The next room is 50% bigger with an EnSuite but will take far less time based on what I have learned doing this room !. In conjunction with the insulation I have added better ventilation to adjoining family bathroom and ensuite in an effort to remove moisture from that end of the house.

hoodie6029

Thanks for all the detailed replies folks. I think you hit nail on the head with the bedroom location. The colder ones have north facing gable walls which is most likely the problem. As you said, no amount of attic insulation will change this.

Cheers folks 👍

The Continental Op

OP if you have it spare you might as well lay it. I'm assuming you are talking about roles of glass fibre insulation. What I've seen even with two layers is that you can end up with gaps or areas where the insulation is a bit thin so I'd put the spare so it covers any joins between the previous rolls and areas that might be a bit thinner.

GreeBo

It really depends on how thick are the roles you have already done and plan to add?

windowcills

Insulation wont make a room warmer, it needs a heat souce, maybe lower the stat on rads in other rooms and turn boiler on for longer

This sounds like a waste of fuel but boilers work better if hot water leaving the boiler is only allowed into cold rads, the cold water from these rads will suck more heat from the boiler as it passes through