Ive built DIY cost calculators - looking for feedback

[noseall]

Regarding part L building regs, I seem to remember that if the cost of insulation exceeded savings over a certain time you could be exempt.
Don't know if this is still current

Yes, the 15 year payback exemption, though this has to be documented (pay for a SAP calc report), etc.

 

[noseall]

Most DIYers have little knowledge of all the materials you need, how costly some of them are and how long, realistically, a professional will take to do a job properly.

True. My extension quote checklist is about 120 items long. Some have subsets. The 'roof' bit has 30 odd items in the subset. I have added to the list over the years.

 

[motorbiking]

Regarding part L building regs, I seem to remember that if the cost of insulation exceeded savings over a certain time you could be exempt.
Don't know if this is still current

15 years - if it fails that test or the other criteria then its subject to U 0.7 “target”, which is 25mm of celotex on a 9" wall with PB. You can also get exemption based on function and technical challenges which include risk of condensation.

 

[noseall]

If the rest of the house doesn't meet any of the new regs, I see little benefit in one wall in a room being renovated making any real difference to the rest of the U- values of the home.

Why bother insulating any extensions, utility rooms, garage conversions?
A large percentage of extensions are insulated to a far better standard than the house they are attached to.
Insulating an outside wall of say a bathroom, could save you having to fight black spot mould for the next decade.

 

[Highway Man]

Why bother insulating any extensions, utility rooms, garage conversions?
A large percentage of extensions are insulated to a far better standard than the house they are attached to.
Insulating an outside wall of say a bathroom, could save you having to fight black spot mould for the next decade.

Yes sounds reasonable