Building your own house: How to DIY insulation

Part way through the ceiling fit-out, The Lego Engineer decided to help out.

Part way through the ceiling fit-out, The Lego Engineer decided to help out.

We've all been told that insulation makes your house warmer and more efficient. And thanks to past and present Government schemes for homeowners and landlords, even some of those fridge-flats inhabited by students in Dunedin have some insulation now. 

But I haven't ever lived in a house that had the full monty insulation treatment. When I put a new roof on our current house, I paid for my roofer friend (thanks Darryl) to put some insulation in. And when we could afford it, we insulated under the floors. But it's an old house, with old wooden windows, and not a scrap of insulation in the walls.

So after these past couple of nights of stuffing insulation, I'm excited about how the new house is going to feel.

Doesn't take much to get you excited then?

Indeed. I noticed a difference almost straight away. Even with only building paper on the walls (still only building paper, argh!), putting the insulation in made the place not only warmer on the dark and stormy nights I was there, but also quieter.

So what are you using?

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One cut and its ready to put up.

Here is the other bit I got excited about. I've put insulation in before, and it pretty much sucked. But using Earthwool Glasswool was honestly super easy.

Firstly it doesn't get up your nose and make your skin scratch like a nasty itchy scratchy thing (if you've put insulation in "back in the day" you'll know what I'm talking about). It also comes in sheets which are the right size for standard studwork (so there wasn't that much cutting to do) and it cuts with ONE slash of the knife.

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Last time, it took forever, this time it took me, on my lonesome, less than an hour to do an entire room.

So you can do it yourself?

Totally. In things to save you money, putting insulation in would be on my top 10 list. It takes time, sure, and the ceiling did take longer – Mr Building Boxes and our friend Jean Sebastian worked from 9am-3pm on Saturday, and then with another two friends, Ben Lampen and Ben Peckham, from 1pm-4pm on Sunday.

But there is more ceiling than wall in the house, and they were fighting gravity so had to strap everything as well. 

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The ceiling took longer than the walls but still went quicker than we thought it would.

I should also note I think my "she'll be right" Kiwi philosophy probably sped me up – I started out measuring and marking my cuts, as instructed by Mr Building Boxes, but quickly realised I could work out the sizes by eye. 

Still, in the grand scheme of things that's not too bad a time commitment. It's pretty straightforward – there are even heaps of resources on the internet to give you (super perky) instructions. And it saves thousands.

And R-values?

If you have been through the building consent process (or you're in the midst of it) you'll know you need to get a certain R-value throughout the house to meet criteria.

For those of you completely lost and not sure how to tell your R-value from your X Factor, it's simply a matter of numbers. The higher the R-value of your insulation (and the same goes for U-value for windows if you're looking at double glazing etc), the better the effect. 

We have slightly thicker external walls, and so have used R3.2, which, ironically, is cheaper than a lower number.

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It took less than an hour to fit this room.

The reason, Mr Building Boxes tells me, for this seeming discrepancy (usually better is more expensive, right?) is that the lower R-value in the 2.6 and 2.8 also comes with a corresponding increase in density for the product, so it can be squeezed into standard 90mm walls. There's more product, packed into a smaller space. So it's more expensive.

In the ceiling, we have maxed the heck out of the R-value dance. Up there we've got R5.2. The reason is because we have a skillion roof, topped with black corrugated iron.

The roof is going to get HOT, and cold, and to regulate that puppy we want to get some seriously thick insulation going, all towards getting as close to the Passivhaus standard as we can afford.

So, you're tucked up all nice and warm?

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The strapped and insulated ceiling.

Indeed we are. Although we've still got downstairs to strap and line with Dritherm – similar to Earthwool Glasswool, but specialised for our concrete block walls. And just in time. 

Moving forward, the cladding is finally arriving on Friday – if it would only stop raining we might actually be able to get it up …


* Introducing the family and the build

How to price a new build

How to find a builder

How to get resource consent

How to work around rain

How to: concrete foundations

How to: build an outside office

How to: sell your own property

How we sold our house by ourselves

The truths of building: you're bound to change your mind

Timber framing goes up

How to cope with the stress of building a house

A baby, an apple tree & a broken arm

Where does a roof shout come from?

When an inspector calls 

How to: Build a house in Nepal

What you need to know about windows

Should you go for polished concrete floors?

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