roof seen on house 100k built?

[CalvinHobbes]

Hiya, I was watching a programme on you tube and saw the householders use an industrial roofing, large panels topped with tin on top of polystyrene . It went on fast and was cheap. No idea how insulating it is...

[JohnMo]

You can get down to 0.1 u value, but that is not cheap. General buildings regs u values is cost effective.  Basically a SIP, with metal either side instead of wood

 

Edited December 10, 2021 by JohnMo
More details

[SuperJohnG]

We put these on my mums garage, they were Kingspan units but didn't know if they were suitable for a house. 

[Dudda]

Kingspan insulated panels are the most common available form of these. Almost every sports hall, industrial unit and warehouse are made of these. They're quick and easy but I wouldn't call them cheap or pretty. The other issue is I think they're very poor acoustically. Driving rain echoes through them and you won't get a great nights sleep. Noise isn't usually an an issue in any of the above places they're used.

[CalvinHobbes]

Thanks for the replies.

?Well my head is already deeved with my husbands snoring so that's a definite no go then.

[SteamyTea]

3 hours ago, CalvinHobbes said:

deeved

Had to look that up.

[markocosic]

Pigeon feet are also bloody loud on these roofs. Kid brother replaced felt roof with kingspan panels because bollox to felt/add insulation and the resin of ok but the pigeons are flipping loud!

[kxi]

@CalvinHobbes  Our building including roof is clad in standard KS1000RW Kingspan panels using 150mm quadcore insulation.

https://www.kingspan.com/gb/en-gb/products/insulated-panel-systems/insulated-roof-panels/quadcore-trapezoidal-roof-panels-ks1000rw

 

It is unusual for a house, but very common for other building types. There's another buildhubber who self-installed them on their dairy conversion roof.

 

We don't live in it yet, but so far my quick summary:

- Can be very insulating and is inherantly thermal bridge free, though you need to detail this at the edges to avoid the metal thermal bridge of the inner liner

- In theory can be very airtight, but there are some issues getting this detailled right

- Looks just like metal roofing i.e. very neat, and available in large range of colours, but likely not going to be accepted anywhere but rural I'd guess

- Can easy drop in insulated plastic rooflights anywhere. These are not see though but allow you to have natural light wherever you like (subject to planning etc) https://www.kingspan.com/gb/en-gb/products/daylighting-systems/rooflight-systems/daylite-trapezoidal-rooflight-plus-ks1000-dltr-plu

- A bit noisy in the rain it seems. If you had an additional layer underneath i.e. plasterboard ceiling, not sure how much this would attentuate this. Crossing our fingers on this one, but many people live in metal roofed houses, and rain noise is one of the sounds people play to help them sleep

- Cost effective considering you get all the layers in one go - you get the whole roof build up for the same price (perhaps even cheaper) than a seperate metal roof

- Fast to install and in theory fairly simple, but likely not something most builders have done (our cladding was done by firm that does loads of it)

- Lightweight and partly self-supporting meaning you don't need as many purlins

- Penetrations are tricky, but not impossible

- Don't use them for walls (long story)

 

 

[Gordo]

I can’t say I notice any significant rain or birds noises on composite roof cladding. Be very careful to make sure vertical over lap joints are well sealed and screwed to avoid condensation at joints. We had a problem with this in a sports hall  and thought it was an intermittent leak which couldn’t be found. Turned out to be condensation but the amount of moisture was incredible so I was sceptical at first. Not so bad in an open building but not so good in a dwelling 

[kxi]

5 minutes ago, Gordo said:

Turned out to be condensation

 

This is def worth noting. The panels are a 100% vapour barrier so if they are added as part of a multi-layer roof/wall build up (like in a house) you have to make sure the parts of the wall/roof inwards are very vapour open to allow drying inwards i.e. no poly sheets or foil-backed plasterboard etc as the moisture would get trapped. Topic for another day, but I've found that it's increasingly common for US buildings to be vapour closed on the outside and aim to dry inwards not outwards. Though if the panels are thick i.e. very insulating, and the building is airtight, then the metal inner liner shouldn't get cold and so condensation shouldn't be a problem (I'm hoping).

 

Another source of mysterious leaks is apparantly if the sheets are laid in the summer the metal expands and bows the panels very slightly upwards. The panels are so strong that screwing them down doesn't remove the bow (and you'd strip the fixings if you tried too hard). When weather cools, the panels lie flat again and the fixings stand very slightly proud of the roof - just enough that the fixing hole is a water path straight through the panels. We had this in a couple of places with just a drip coming through. No problem to fix, someone just needs to tighten the fixings, but it's something you might not even notice if you covered up the roof from the underside before the weather turned cold, and then have a persistent hidden leak.

 

So you shouldn't just swap them out in place of a regular roof without thinking carefully about what else might need to change, and the designer & installer has to be aware of the potential issues.

[Gordo]

3 minutes ago, kxi said:

I've found that it's increasingly common for US buildings to be vapour closed on the outside and aim to dry inwards not outwards.

The US do it the opposite way around because it is warm out side and colder and air conditioned inside. So tenancy for moisture drive is reversed and VCL should on outside (VCL should always go on warm side of insulation). 
 

the problem we experienced was in cold snaps the cold humid air came in through panel joints, condensed in the joint and then dripped. This was happening in multiple locations and was a surprisingly expensive repair. The building was approximately 20 years old so don’t understand why it happened after this period 

[kxi]

2 minutes ago, Gordo said:

the cold humid air came in through panel joints, condensed in the joint and then dripped

 

Our panels have the internal seals inside the joint top and bottom which should keep it air & water tight (each end is also capped off, which now i think about it might not be done well). The cladder warned that IF the outer seal ever water leaked you don't want to trap anything inside them. Hence they sometimes omit the inner seal to allow the joint to drain out. My problem is the inner liner is the air barrier and I want it very airtight, so no way I could omit the seal, so it may just trap any leaks. I'm in two minds about whether we'll need to air tape / sealant it as well from the inside but hope not to.

 

I guess in your case it might have been the outer sealant became brittle after 20 years and started to let in air? Hopefully someone will have come up with a good solution by the time mine starts to leak.

[Gordo]

19 hours ago, kxi said:

 

I guess in your case it might have been the outer sealant became brittle after 20 years and started to let in air? Hopefully someone will have come up with a good solution by the time mine starts to leak.

The outer metal cladding projects the panel to overlap adjoining panel. The double sided tape failed (other issues as well). Only proper remidy was to relay panels with a butyl rubber tape between overlap (seem that tape is a premium option which is often specified)

[saveasteading]

On 10/12/2021 at 09:44, Dudda said:

think they're very poor acoustically.

 

Composite panel (sandwich of metal around PIR) is pretty good acoustically. Noise is more likely to come from skylights.

 

I think the noise 'issue' is touted by tile manufacturers.

21 hours ago, kxi said:

Can easy drop in insulated plastic rooflights anywhere.

Yes but they are inferior thermally and not suitable for houses. Any gap in a composite metal roof (roof-light, flue) is a big risk for weather sealing, depending too much on mastic.

 

19 hours ago, kxi said:

they sometimes omit the inner seal

This is a different thing. Composite panels only get sealed from above. This sounds like 'built up' roofing , so cladding insulation, cladding. 

Both skins should be sealed.

 

20 hours ago, kxi said:

if the sheets are laid in the summer the metal expands and bows the panels very slightly upwards.

Haven't heard that one before, and have had 10,000m2 used on roofs and walls.

There is an issue with screws needing retightening, but I  think this is the cladding bedding down when walked on/ wind chatter.

 

19 hours ago, kxi said:

outer sealant became brittle after 20 years

The best sealant (in tape form) never goes hard if protected from sunlight, but it costs a lot more.

[kxi]

3 hours ago, saveasteading said:

they are inferior thermally

 

https://www.kingspan.com/gb/en-gb/products/daylighting-systems/rooflight-systems/daylite-trapezoidal-rooflight-plus-ks1000-dltr-plu

The ones we have (above link) are rated at 0.8W/m2k, which is as good as triple glazed windows marketed for passive house. However, given kingspan's track record, it's possible this rating is not true, or that the construction is vulnerable and so more liable to not perform.

 

 

3 hours ago, saveasteading said:

Any gap in a composite metal roof (roof-light, flue) is a big risk for weather sealing

 

I guess so, but they use the same lapping with a seal as the metal panels, so if the skylights are a risk, so are all roof joints in this kind of cladding? These rooflights are very common in commercial and industrial buildings and it would be surprising if they were so fundamentally flawed that all these buildings were bound to fail early. It is true the plastic and sealant is UV exposed so more vulnerable over time than the metal panels.

e.g. side lap (on thin version)

 

end lap:

 

 

 

3 hours ago, saveasteading said:

Composite panels only get sealed from above

 

Page 7 of the Kingspan installation guide for the KS1000RW panels shows how sealant can also be applied at the base of the panel side joint, as it was in our case. This provides our air and vapour seal on the panel inner face. I am concerned it's not going to be airtight enough, hence thinking about additional taping.

https://www.kingspan.com/gb/en-gb/products/insulated-panel-systems/downloads/kingspan-quadcore-rw-trapezoidal-75mm-no-faws-roof

 

 

 

 

 

Edited January 6, 2022 by kxi

[saveasteading]

2 hours ago, kxi said:

rated at 0.8W/m2k,

Good info thanks.

The detail you show is better than many, But you need a bigger area than with glass for the same light, so more heat loss.

2 hours ago, kxi said:

same lapping with a seal as the metal panels

Yes, that is the best detail. But the best steel will last a lot longer than the best polycarbonate (which is much better than fibreglass). Also the screws pull the steel very tight, whereas you have to be gentler and use extra big washers over the plastic.

I know that there are many more leaks at skylights than at metal joints. Plus birds sit and peck at the plastic.

2 hours ago, kxi said:

how sealant can also be applied at the base of the panel side joint

That is new to me. there is a foam compression filler there, so they seem to be acknowledging some concerns.

 

Never had any air test problems due to standard cladding, only when special details had to be formed for aesthetics.

 

When I read your piece I hadn't thought of using these rooflights in a domestic setting, so was thinking of plonked on feature skylights.

I agree that metal cladding can look fine for domestic, even in an urban setting, as long as it is like this profile and grey, as it looks like an old zinc roof, only modern.

 

Some of my concerned comments are related to flattish roof slopes, and diminish on domestic looking slopes, but composite is horrible to lift and fix on steep slopes.

[Gordo]

On 07/01/2022 at 00:08, saveasteading said:

which is much better than fibreglass.

I would have thought fibreglass would have superior to polycarbonate. Do you mind I ask what’s your thinking

[saveasteading]

38 minutes ago, Gordo said:

fibreglass would have superior to polycarbonate.

I mean translucent fibreglass (grp) rooflight panels, to the same profile as the top sheet, as opposed to the multicell polycarbonate as shown here.

For half decent insulation with grp panels you need 2 of them and an extra layer between of polycarbonate.

 

I didn't mean filling with fibreglass quilt, or a comparison with an insulated area of roof.

[Gordo]

1 hour ago, saveasteading said:

I mean translucent fibreglass (grp) rooflight panels, to the same profile as the top sheet, as opposed to the multicell polycarbonate as shown here.

For half decent insulation with grp panels you need 2 of them and an extra layer between of polycarbonate.

 

I didn't mean filling with fibreglass quilt, or a comparison with an insulated area of roof.

Yes I realised you ment profiled GRP panels. Yes I guess cosmetically, thermally and for light they would be inferior to multi cell polycarbonate for domestic, but for industrial cladding better IMO.

Edited January 11, 2022 by Gordo