building regs certificate doubt

alwaysquestioning

I am in the process of purchasing a flat where external wall insulation (EWI) has recently been installed.

According to Building Regulations, to comply with Approved Document L, at least 120mm of insulating material (in my case, Rockwool) should have been applied. I checked the specifications for the material used, which confirm that a minimum of 120mm is required to achieve a U-value of 0.30 W/m²K.

Initially, I assumed that the seller had not obtained the Building Regulations completion certificate. However, to my surprise, the certificate has indeed been issued.

From the planning application, the original design did specify 120mm of insulation, which might explain why it was approved. However, in the end, only 50mm was installed, which is significantly below the required thickness.

However, I still have some doubts:

1. How is it possible that the Building Control Officer (or the relevant authority) approved the work and issued the certificate if the insulation thickness does not meet the required standards?
2. Does anyone know how these Building Regulations inspections and certifications actually work?
3. What potential issues could I face in the future, if I decide to sell the property, given that the insulation does not meet the required specifications despite having a Building Regulations certificate?
4. would you go ahead with a flat purchase in this case? (there is not any warranty on the walls insulation even if it is brand )

Thanks!

FreeBear

There are cop-outs in the Building Regulations. You may not need to achieve the recommended u-value if it is not technically possible or the simple payback period exceeds 15 years. In these situations, the regulations state that one should do the best possible. Building Control will also accept thermal improvements made elsewhere to offset the reduced performance of the walls.

If Building Control have issued a certificate for the works, it should mean that they are satisfied that overall, the project meets their agreed targets.

alwaysquestioning

thanks @FreeBear ; How do you justify the discrepancy between the approved planning permission (120mm insulation) and the final installation of only 50mm?

Isn’t it contradictory to approve a 120mm installation initially and then issue a certificate despite only 50mm being installed?

I am perplexed about the whole building regs thing  

FreeBear

alwaysquestioning said: Isn’t it contradictory to approve a 120mm installation initially and then issue a certificate despite only 50mm being installed?

I am perplexed about the whole building regs thing  

One would have thought that there would have been some discussion about cost vs savings prior to the application. It is possible that the developer discovered some technical difficulties or the material costs jumped significantly post application. Unfortunately, you wouldn't be privy to and discussions between BC and the developer.

Every time I look at the building regs documents, I find little nuggets that don't make sense or some loophole to avoid full compliance.

Doozergirl

There are different types of insulation and different thicknesses have different u values. 

For EWI, I'd usually expect to see some type of solid insulation rather than rock wool.  Are you sure it's rock wool? 

Also, the approved documents would specify the required u values, not what product needs to be used to achieve the u value, so what are you reading? 

FreeBear

Doozergirl said: For EWI, I'd usually expect to see some type of solid insulation rather than rock wool.  Are you sure it's rock wool?

From an earlier thread - https://forums.moneysavingexpert.com/discussion/6588332/external-insulation-without-building-regs - The EWI system (K Systems) is a mineral wool slab with a cement based outer layer.

Excellent fire resistance, adequate thermal performance (if thick enough), and claims to be suitable for solid walls.