How to top up ceiling insulation?

[cludelessdiwhye]

We have an old house that has what appears to be about R3 insulation in our roof.  We are in Sydney and find the house hot in summer and colder in winter, so I wanted to top this up, by adding another layer on top of the existing layer.  I have 3 questions:

1) the joists are already filled with the insulation.  Can you place further insulation on top, so that it sticks above the joists? I am aware that compressing the insulation down is not advised (as it reduces the r values).  A solution would be to run the insulation over the top of the joists (but then I don't get how you can walk around after it is put down).

2) there are a range of spots where there is no insulation, including above an internal wall (I suspect in a previous iteration of the house this was an external wall at some point).  Should insulation be put over the top of this?

3) we have a manhole cover with a ladder.  My understanding is that the presence of uninsulated areas has a disproportionate impact in reducing the effectiveness of the ceiling.  Are there any ways to improve the thermodynamics of this area (I couldn't see how this would be possible but thought it worth asking,

Thanks in advance.

[EricL]

Hello @cludelessdiwhye 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about ceiling insulation.

This question was asked awhile back, and I suggest having a quick look at the discussion as it answers a variety of questions - How to add extra ceiling insulation? by @monkeybaby. In order to walk over the insulation, I suggest bringing some plywood strips half meter wide to serve as a temporary floor to walk on when getting out. Another option is to start at the ends and then coming towards the manhole of your ceiling.

In regards to those blank spots with no insulation, it would be best to cover them so that you have a uniform cover in your ceiling. In regards to your manhole cover, it all depends on how creative you can get. One way to keep the insulation in place on the cover itself is to use straps. It does not have to be very tight just firm enough to hold the insulation in place even if the cover is moved. Another option is to create a lightweight frame on the cover to hold the insulation in place.    

Let me call on our experienced members @Dave-1, @Nailbag and @AlanM52 for their recommendations.

Please remember to wear personal protection such as long sleeve shirt, pants and closed toe shoes along with glove, goggles and a mask when handling an installing insulation. 

If you need further assistance, please let us know.

Eric

[AlanM52]

Hi @cludelessdiwhye,

Over the years the ROCKWOOL insulation granulate in the roof of our 1971 house had collapsed to the point where it looked like carpet so I just laid down Pink Batts on top of that. I am 6' 2" and did not fancy crawling trying to push batts out to the edge so mate on the roof would push a tile back then grab the batt, pull it over and lightly tamper down with a push broom.

In your case I suggest lay the insulation the same way no matter that it sticks above the joists and they will still be visible to safely walk or kneel.

You can cover any blank spots but check, maybe the were left like that for electrical or plumbing reasons.

For the manhole I cut a batt to size and glued it down.

You should be able to cover that internal wall area but maybe post a few photos so we can have a look.

Cheers

[Dave-1]

Good morning @cludelessdiwhye 

I am unsure wether I would pull out the old insulation and replace with new to get the nest effect. That way you will have a consistant depth of insulation at the rating you expect. I have extremelly dodgy insulation scattered across my ceiling and think I would be taking the path of remove and replace. 

You could get a heat senser gun and check out what is there now, then lay some insulation over what is there and check again the next day? Sounds convuluted but may save you having to remove a bunch of old insulation.

I would also recommend you turn the power to the house (not just the lights) while climbing around inthe ceiling space, making sure not to cover any downlight fittings.

Dave