Roof sarking for IP?

Hey guys,

I am building my first IP. Construction has already began on the property, and now the builder is offering to do roof sarking with no builder margin at $1,262.

My preference is not to spend any more extra on this IP (as we have found rock on the site), but do you think this would be worth it?

From what I understand the benefits include the below. I am more worried about points #2 and #4.

The property is about 15km from Canberra CBD. It is a 4bed at 138m2 living with concrete roof tiles. The EER on the approved plan is 6.9 (I'm assuming this is without sarking). Most of the windows in the house faces West and North.

1. Improves thermal performance by shielding your new home from up to 97% of radiant heat.
2. Protects the frame of your new home from adverse weather during construction.
3. Provides a secondary form of bushfire ember protection for the roof of your new home.
4. Reduces the amount of dust and storm driven rain from entering your roof cavity. This will protect your new home from mould growth and ceiling staining/damage.

Thanks guys!

 

How does your designer achieve thermal performance without sarking if it knocks out 97% of radiant heat transmission?

Oh that's right, it's the tenant's problem to heat or cool the house. It'll probably save that amount in energy bills in the first year.

 

Just spend the $s on sarking. There is generally no problem then with small leaks or roof tiles that may leak a little over time. It is good insulation also. $1,200 is peanuts really - just do it!

 

If you want to live in the house in the future this will be something you will be glad was done. Most tenants like a warm house. 1200 something seems incredibly good value.

 

Also, if it provides protection from bad weather and bush fire events it may prove VERY cost effective. Cheaper than a new roof and vacant property.

 

Thanks guys! Appreciate the feedback.

I'm not very technical and don't currently have sarking in my PPOR. Does anyone know if the thermal/insulation benefit is really as good as claimed, and is it the same for concrete tiles (as oppose to Colourbond)?

Is there different types of sarking? The exact description the builder has given me is "Heavy duty sarking (includes anti ponding board to zero eaves if any)" - is this OK?

 

Also, the cost does not include any roof ventilation. From what I have read, sarking also prevents heat from escaping at night, which is where roof ventilation would help?

 

Did you get an energy rating report or approval as part of the overall approval?

How was the energy rating achieved?

Personally, I'd give it a miss. If it really becomes an issue with the tenant then just get some insulation blown in for around the same price or even some insulation batts, but I'd hold off for now.

Oh, I forgot to add. Points 2 and 4 are bulls**t. In fact even point 4 is bulls**t.

 

my previous ppor now ip has cement tiles and no sarking. The dust storm we had a few years ago left everything within the roof space covered in red dust, some dust filtered through the new downlights into the house.
Current ppor being renovated has thermal (builders) blanket under colourbond, which is sarking with insulation on the top side.I paid approx $80 per roll.Bradford Anticon - insulation for homes with metal roofs Along with insulating the roof space it also stops a lot of noise.I think this might have become the standard now. It might pay to confirm what type of sarking your builder is using perhaps it is builders blanket.

 

Depending on the state building requirements, I thought sarking was near manditory?
Like Tyvek wrap on new house contructions ....
Happy to be told otherwise
Also, sarking isnt what it once was....
Sarking alone was said to have a R0.5 insulation factor
Combined with a glued on insulation layer often glued to it these days takes it straight to R1.5
These are easily rolled out over the roof battons and held in place when the corrugated iron ifs affixed
Well worth the small cost (for the sound dampening during pelting rain at night)
And helps protect plaster against any leaks (as when installed properly water runs down into the guttering

 

Like this today

Old tile roof removed, old bitumen sarking under, new battons for corrugated iron installed.
On the far right you can see the fluff of insulation attached to the new silver sarking rolled out under the new iron roof.
Great for sound dampening.

For roof space venting I'd buy a solar powered vent off Ebay
The one that only operates above 30 deg
Like on hot days/summer when you want it to
Sure, you could have a vent that operates all day in winter sucking out any hot air

 

Hey guys,

So the sarking I have been quoted by the builder does not have any insulation on the top side. I have read many threads where people have been happy with their Anticon, which I believe do have the insulation attached to the foil.

If the sarking is foil only, am I going to get any considerable/noticeable thermal improvement?

And is it OK to have sarking without any roof space ventilation, e.g. whirlybird?

Also, my roof are concrete tiles so rain noise is not a concern for me.

Thanks!

 

Anti con is used for metal roofs to stop condensation, reduce sound transmission and reflect radiant heat.

If your roof is tiles, you wouldn't use anticon. Instead you'd use sarking (i.e. foil either the thin stuff or the slightly thicker stuff that has a thin layer of insulation giving a slightly higher R value. I'm amazed that sarking isn't mandatory in the ACT!

From the Bradford’s site re. BCA:

'Sarking and the Building Code of Australia
It is mandatory under the Building Code of Australia (BCA) that all tiled residential roofs, regardless of roof pitch, with a rafter length greater than 6 metres must be sarked.

CSR recommends that all tiled roofs with a pitch of less than 20° are sarked and the BCA mandates this requirement for rafter lengths greater than 4.5 metres.

As a general guide, it is considered good building practice to sark all tiled roofs as it helps to address the requirement within the BCA to protect the building from the entry of external moisture.'

Also, just make sure that extraction fans from the bathrooms etc are vented to the external air and not into the roof.

 

Thanks @Joynz. With the sarking, seeing that it is foil-only and does not have the insulation material attached - would it still give me the same significant radiant heat reduction?

And sorry for the dumb question, but I think my rangehood and extraction fans are not ducted externally - what would be the impact if they are vented into the roof space?

 

It is the reflective quality that prevents the radiant heat. It’s a different kind of insulation from batts but it is equally as important - especially in summer.

The effect of venting into the ceiling can be to create condensation. With a sarked roof you will have to vent to the outside air - according to the BCA (NCC). This is pretty standard these days anyway as we try to make houses more airtight.

I have altered my previous post slightly - with a quote about the BCA - have a read.

 

Got it! thanks @Joynz!

Another question if I may.. is it OK to have sarking without any roof space ventilation, e.g. whirlybird?

 

Whirlybirds or other roof ventilation are not required (and not that effective). If you do want fans, then you should get solar powered ones as they are much better at extracting air.

But ACT is a 'heating, climate where most of the year you need to keep the heat in!

Can I suggest you consult the online Your Home Technical Manual'. Full of great information.

 

Thanks @Joynz! Yeah I only asked about whirlybird because while researching sarking I often came across ppl who said things like “make sure you get a whirlybird” or “you’d need 2 whirlybirds at minimum” etc. Some posts I came across seem to suggest that sarking makes it harder for the hot air in the roof to escape and therefore ventilation would help.

But it’s good to hear that sarking does not make ventilation a necessity !

 

@Bernado
A form of roof ventilation is a good idea
But as @Joynz said, most of the year you actually want to keep the warmth in.
So, there are solar powered roof extraction fans (Ebay) that have an inbuilt thermometer and will only operate when the internal temp reaches 30 deg

 

Thanks guys! I think I have decided to go with the sarking.

A related question: what do you guys think of wall sarking? I believe I do not have this in my inclusion list. My house has dark bricks and dark roof tiles. It’s on a corner block and the majority of the walls and windows directly face west. Would wall sarking along the western wall do much to reduce the heat?

If I have to choose between roof sarking or wall sarking but not both, which would you recommend for best bang for buck?

Thanks!