Crazy Rafter Roll insulation cost

[MortarThePoint]

Is Mineral Fibre rafter insulation always so expensive?

 

I've been quoted £18/m2 for 100mm Knauf Rafter Roll 32 and that just doesn't make any sense:

• Same seller sells 100mm Dritherm 32 for about a third of the price per m2 (£6.70/m2). That's a performant self supporting product as well.
• The same seller lists 100mm PIR which is 50% more performant for £12.91, so cost per performance, that's less than half the price of the Rafter Roll. You'd expect to pay a premium for the thinner more performant product.
• All other applications, Mineral Fibre is considerably cheaper than PIR

 

I have spoken to Knauf Technical and they can't comment on pricing. FrameTherm is also recommended for the rafter application so I am looking into that. Isover Metac seems to be similarly expensive.

 

I don't want to use PIR or XPS due to the chemical content. I know that divides opinions, but can anyone recommend a sensibly prices alternative to Mineral Fibre.

[ProDave]

What is the application?

 

I successfully used Frametherm 35 for wall and roof insulation.

 

If it does not need to be self supporting, I paid £20 per ROLL (about 6 square metres) of 150mm Knauff loft roll

[MortarThePoint]

9 minutes ago, ProDave said:

What is the application?

 

I successfully used Frametherm 35 for wall and roof insulation.

 

If it does not need to be self supporting, I paid £20 per ROLL (about 6 square metres) of 150mm Knauff loft roll

 

It is for between (and below) rafters. I haven't had a price yet for FrameTherm but hope it may be my saviour.

 

I spoke to a merchant a couple of years ago who said lots of people staple Loft Roll between rafters ? I don't think that's a good plan 

Edited June 4, 2021 by MortarThePoint

[ProDave]

I was using the loft roll for insulating my sun room floor so it did not need to be self supporting.

 

Frametherm 35 used in my ceiling, self supporting between the rafters before being boarded.  I did one test section where I put a strip in long before I was ready as a test and left it there for 6 months and it did not sag or fall out.

 

[ADLIan]

Beware of extended lead times and price rises. Knauf I believe are on 6 week or more lead time with 14% price rise due soon.

[MortarThePoint]

9 minutes ago, ADLIan said:

Beware of extended lead times and price rises. Knauf I believe are on 6 week or more lead time with 14% price rise due soon.

 

Thanks. I have seen the long lead times but thankfully none of it is urgent.

[MortarThePoint]

@ProDave What's this bit?

 

[ProDave]

That's a batten to catch the edge of the OSB sheet about to go on.  OSB sheeting first, air tight membrane, battened service void then plasterboard.

 

In my original picture you see the batten running all the way down and behind the first bit of OSB already in place.

[MortarThePoint]

38 minutes ago, ProDave said:

That's a batten to catch the edge of the OSB sheet about to go on.  OSB sheeting first, air tight membrane, battened service void then plasterboard.

 

In my original picture you see the batten running all the way down and behind the first bit of OSB already in place.

 

Have to taped the batten though?

[ProDave]

32 minutes ago, MortarThePoint said:

 

Have to taped the batten though?

The batten is just to secure the OSB.  Air tight membranes and taping go over the top of the OSB detailed here http://ardross.altervista.org/Wilowburn/insulating-the-roof/

[Declan52]

I also used frametherm for my room in the roof insulation. If it's cut to suit the gap in the rafters then it won't go anywhere. Like @ProDave I left a section not boarded for a few months waiting on plumbers to work their magic and it never moved a mm.

[MortarThePoint]

FrameTherm sounds like a good choice, I've also seen FactoryClad is a lot cheaper, but may be difficult to cut to width.

 

I'm taking a look at Actis Hybris which I have to admit to being a bit sceptical about. I need to understand it a bit more, but I might be being a luddite.

[saveasteading]

I had useful , off-the record,  advice from a national insulation supplier.

 

For the best price, never mention any trade names.

 

For example,  if you say you asked for a price for 'Celotex or an alternative', then they had to give the quote for only Celotex, or at least not undercut it.  It was an agreement with the suppliers.

I think the idea was that if an Architect specified a product, and the supplier may have helped with the design, then they would get the order. 

 

That gets difficult sometimes , how to ask for rock wool without saying Rockwool.

 

That may not be the issue in your case, but could be.

 

Also I learnt that they charged different prices in different areas, even if it all came straight to site in one big load from the factory. Just because they could.

75% discount in Oxfordshire, but only  65% in the South East, I seem to recall.

 

I think the same, re names,  can apply to other products at builders' merchants. 

 

Do tell us the best prices you get , please. We can all save each other a lot with the benefit of insight.

 

 

 

 

[MortarThePoint]

31 minutes ago, saveasteading said:

For the best price, never mention any trade names.

 

Interesting and very helpful, thank you. The whole pricing thing is really opaque and leaves me permanently thinking I'm left paying over the odds. I'd prefer greater transparency, but the closest I can get to that is SPONS and that has never been more out of date than under the current climate.

 

I can remember when I first got my trade account at Jewson, I walked up to the counter with an arm full of plumbing fittings and the woman at the till punched in some numbers and gave me the price that was over double Wickes. I said that and she said that it was Osma fittings etc and that's much better than Wickes, though she would take a look and it came straight down to a bit under the Wickes price. I had naively hoped that having a trade account meant the end of the haggle, but how wrong I was.

[ProDave]

1 hour ago, saveasteading said:

For the best price, never mention any trade names.

 

For example,  if you say you asked for a price for 'Celotex or an alternative', then they had to give the quote for only Celotex, or at least not undercut it.  It was an agreement with the suppliers.

I think the idea was that if an Architect specified a product, and the supplier may have helped with the design, then they would get the order. 

 

That gets difficult sometimes , how to ask for rock wool without saying Rockwool.

Mineral wool, Glass wool or Earth wool should cover that?

[Thedreamer]

@MortarThePoint another one here that use Frametherm. I use Quinn therm in other areas but if I could go back I probably would have done the whole lot in Frametherm. Less messy and easy to cut and store. 

 

[saveasteading]

but the closest I can get to that is SPONS and that has never been more out of date than under the current climate.

 

Spons is usually very conservative/ expensive. It is useful for an approximate guide for an estimator needing a price for an item in a hurry, and I guess it could be deemed to include sundries and a level of sub-contractor margin.

(I once had to price a 3 storey office on the basis of Spons x a factor. I think we went at minus 20% and made a lot.)

 

I used to use a 3 year old one, being more accurate I felt ( and a discounted bargain itself) 

Interesting that you think they are under-priced now.

 

 Earth wool:   

I thought Earth Wool was a Knauf trade name.

 

 price that was over double Wickes.

I had the same with TP. Asked for a price for a dozen various 100dia branches. Got told to pick out what I wanted then they would put them through the till.  NO, I want a price.

The price was 3 x the toolstation price, even though both in same ownership. Same excuse...quality Osma v unknown. That may be right to some extent but the toolsation ones worked fine.  12 x £11 just like that.....not saved, but not wasted.

The manager then explained that they were as exasperated as we were that they were being undercut by their own owner.

 

Another example was MDF. We wanted 2 pallets of it and a merchant quoted a price that was more per board than a single from Wickes.  So was easy to quote the Wickes price as a starter...and of course they then knocked a lot off. It is cheating.

Once last because it annoyed me so much. Jewsons, bag of washers (for shims) £8.   Went to another branch for more £36.  Same product but massive margin (500%??) They lost our account because of that.

 

Moral;   know the price before you start. Wickes is handy but limited.

 

 

[ADLIan]

Earth wool is a trade name. Google ‘timber frame roll’ for alternative manufacturers

[saveasteading]

Or 'cavity wall batt''/slab/insulation if you need the waterproof kind.

[MortarThePoint]

54 minutes ago, ADLIan said:

Earth wool is a trade name. Google ‘timber frame roll’ for alternative manufacturers

 

34 minutes ago, saveasteading said:

Or 'cavity wall batt''/slab/insulation if you need the waterproof kind.

 

One thing I wonder though is if Rafter Roll has controlled expansion to ensure it doesn't expand up and touch the roofing membrane. There's supposed to be a 50mm gap left. SHould have gone the counter batten route, but too late now ?

 

@ProDave your FrameTherm didn't look to puff up whereas @Thedreamer yours did. Any thoughts on that?

[ADLIan]

Low density loft insulation is compressed more than cavity/rafter/timber frame insulation. All should expand to stated thickness once unwrapped but over or under expansion should not be tolerated. Complain to manufacturer if this happens.

[Thedreamer]

14 hours ago, MortarThePoint said:

 

 

One thing I wonder though is if Rafter Roll has controlled expansion to ensure it doesn't expand up and touch the roofing membrane. There's supposed to be a 50mm gap left. SHould have gone the counter batten route, but too late now ?

 

@ProDave your FrameTherm didn't look to puff up whereas @Thedreamer yours did. Any thoughts on that?

 

In my photo two different products are being used Frametherm 35 in the walls and Frametherm 32 in the floor. The 32 is thicker product and more expensive.

[ADLIan]

I’m not sure the additional cost of 32 grade is justified in a better u-value when installed between rafters or studs. The thermal bridging in this layer means only a very small decrease in u-value (0.01 better?). 35 grade probably at the sweet spot unless you’re really desperate for that very last bit of improvement.

[MortarThePoint]

On 06/06/2021 at 11:36, ADLIan said:

I’m not sure the additional cost of 32 grade is justified in a better u-value when installed between rafters or studs. The thermal bridging in this layer means only a very small decrease in u-value (0.01 better?). 35 grade probably at the sweet spot unless you’re really desperate for that very last bit of improvement.

 

Good thought.

 

I was also wondering if anyone has used Knauf FactoryClad 32 as I am seeing that for a fair bit cheaper than others.

[JOE187]

    Rockwool Flexi in 600mm or 400mm  x 1200mm at 100 or 140mm thickness  would be my recommendation.