External Wall Insulation: Rockwool, Phenolic or EPS??

C

coolaboola

Registered User
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Hi folks,

I know there are a few posts out there about external wall insulation but none quite address the query I have - I hope you might be able to help.

I've got three quotes for external wall insulation on my 3-bed end of terrance. They are all very close in price (all around €13,000). One supplier provides EPS (expanded polystyrene), another phenolic and the third rockwool.

Which is best? I'm inclined, from what I've read here to date, to chose rockwool. However, I'm concerned about its water absorbency - I don't want it absorbing like a sponge in the event of rain during installation or degradation of the integrity of the render system. Also the rockwool contractors are recommending a slightly thicker depth of insulation than the EPS or phenolic contractors.

I'm also curious, given that rockwool and phenolic are considerably more expensive than EPS, why the EPS quote is nearly equal to the phenolic and rockwool quotes... but that's something I should raise with the EPS contractor.

Hope you can help...
 
Are you sure its going to cost €13.000. we got ours (detached house) done recently with little bead things for under €1500
 
I posted a reply to this query earlier today, what happened it.
 
I don't know... I hope the technical gremlins fix it. I eagerly await some advice on this (hope the place the contract in the next week)
 
Phenolic foam is the best, in that it has the lowest U value, usually around 0.02w/m2K. EPS is around 0.035 - 0.038, the lower being graphite injected. Rockwool is in the similar range as the EPS. The main differences are to achieve the required overall U valve or R value, you will have to use thicker levels of the higher U valued products. So in cases, where restrictive thickness are required, then you will require phenolic foam to achieve the required R value. (R Value being the overall required value of the total fabric)
EPS is by far the cheapest. Rockwool is a nice material but it will lose some of it's U value over time as it depends on air within it to achieve it's U value. Similar to how fibre quilt behaves in an attic space. New, it's nice, thick and fluffy, 5 years time, half the thickness and a bit limp, 10 years: throw it away. Phenolic foam on the otherhand should last a lifetime. It is also closed cell, in that when it comes in contact with water or moisture, it will not affect the integrity of the material, whereas, open cell materials, such sprayed insulation loses it's thermal properties on contact with moisture.
If cost is an issue, phenolic foam being the most expensive, then you could opt for an in between called polyiso. This has very similar properties to phenolic foam and has a U value of 0.023W/m2K. It is also closed cell. You will have seen it before, such as insulated plasterboard slabs for walls, rigid roof insulation particulary in dormer bungalows, floor insulation, etc.
Either way, you should have a detailed calculation carried out giving the required building regulation U value, each contractor giving you what their product will achieve, what guarantees they will give you and how long it will perform for at this overall R value. Get references and CHECK THEM OUT.
Also most manufacturers of insulation offer free consultation, free calculations, performances, etc. and are extremely helpful.
Check out: Kingspan Insulation, Xtratherm Insulation & Quinn Insulation. All will offer the above service free of charge.

Hope this helps....
 
the IAB certification has been removed for phenolic insulations

always check to see whatever product is being quoted for HAS IAB certifcation.

AFAIK the only products currently still certified are EPS and Rockwool
 
phenolic has been reinstated about 3 months ago on weber certs
 
Thanks very much for replies. Very informative.

Rose, it's deffo circa €13,000 - this is for external wall insulation, not cavity fill (our house is solid concrete block so cavity fill is not an option).

I'm surprised that phenolic has the best U-value. I understood rockwool and phenolic to be equalivaent U-value and cost while EPS has higher (bad) U-value and much lower cost (not, as I mentioned, that this was reflected in the EPS price!). I was concerned about the certification issue around phenolic - what's the background to that (I was aware that it had regained it's certification)
 
ccfc said:
phenolic has been reinstated about 3 months ago on weber certs
Click to expand...

thanks, found it [broken link removed]

wonder what did they to counteract the issue of the phenolic breaking down when wet???

i see a minimum of 5 mechanical fixings per board is required, thus increasing the thermal bridging.

personally id prefer to increase EPS depth to counteract any perceived loss of performance, when comparing EPS with PHS. I see that IAB cert for both EPS and PHS has a max thickness of 200mm. I wonder why as EPS can easily do 300mm.

also the thermal conductivity value of 0.02 for PHS is not assessed as part of the cert and is only down as the manufacturers declared value, not that im challenging that.
 
Thanks for all the advice AAMers. I've opted to go with EPS on the basis of its inherent moisture resistance and its proven track record. (I will be installing some small areas of phenolic where soffit depths require a thinner material) Works due to begin in a couple of weeks. Will let you know how I get on.
 
I don't know what it works out as per m2 . If it's any help, my house is a 1939 3-bed end of terrace (the style that is slightly bigger than the standard Dublin Corporation 2-bed house) I've a small kitchen extension (internal dimensions c. 8' x 10') that is being included in the external insulation. The quote was for c. €13,800.
 
It's never easy...

Less than two weeks before our external insulation work is due to start... Quotes got and accepted, scope of works agreed... Have registered and been approved for SEAI grant... ESB and UPC have been informed and have done their necessaries... Other works that had to be done before the start of the external insulation works are finishing up today... we're all set and ready to rock and roll... toasty house, here we come...

... and now the bloody insulation contractor has pulled out of the job altogther!!

GRRRR!!!!

Am now chasing up the next contractor in line and deciding whether to get them to requote for EPS (their original quote was based on rockwool but I have concerns about it's moisture resistance)

Really, I just needed to vent but am also keen to get recommendations for (good, reliable!!) external insulation contractors who work in the Dublin area.
 

Had this work done earlier this year-dont know what area u are in-we used Insulateyourhome.ie....Kevin is the main man....around €85 per m2 I think...did a good job...but more importantly...found Kevin good to deal with...if u want any other info let me know-but not too technical!
 
You should be very cautious of somebody completing your work for €85 per m2, you should be making sure that you are getting what you pay for, in the case of €85 per m2 you won't be getting much. While it may look good on the outside you should also make sure what is being done underneath the system is done properly. If external insulation is not done properly it can actually have adverse effects on your home ie: increased condensation internally around the windows if the external window reveals and sills are not insulated

Ask your contractor does he?
1. Cut off and insulate all your sills and window reveals
2. Use an extruded polystyrene below dpc level
3. Complete a boroscopic and pull test to determine suitability of the system
4. Use IAB certified products from an approved supplier

If he answers yes to all of these questions then you are on your way.
The best way of finding a competent installer is by contacting them and looking for a list of completed homes for you to go and look at. The homeowners who have had the work completed will be the ones that will tell the truth. Be SMART and do your research it's alot of money but well worth it!
 
Just a little update on this one: Went with the second contractor on my list who agreed to do the job with EPS (their quote was originally based on Rockwool). They're cheaper than the original contractor, more professional and better to deal with so far.

They arrived on site today, a day early (unannounced due to crossed wires, the only hiccup so far). House now covered in scaffolding. Fingers crossed it won't be long til our house will be cosy... I'll keep you posted on how we get on.
 
P.S. pftg5, what's the boroscope and pull test for? Sounds like something you'd do for cavity insulation perhaps? Where would you boroscope and pull for external insulation?
 
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