TA has spec'd 150mm Kingspan TR27 for garage flat roof. Cheaper options?

[flanagaj]

One of the requirements for our build is that I want a garage that is not cold and damp.  As a result the TA has specified cavity walls as per the main house, 150mm celotex floor insulation and 150mm Kingspan TR27 roof insulation.  This obviously comes at a cost and I am wondering whether it is overkill and I could reduce the floor insulation and also the roof insulation a bit.  There is no door connecting the garage to the house.

The garage will be my workshop and gym so having something that is not Baltic during the winter months is the main criteria.  I am also thinking of putting a radiator in too.

Edited yesterday at 10:00 by flanagaj
added image

[Mr Punter]

What is a TA?  The insulation will cost about £35/m2.  I am not keen on the parapet wall as they are just another weak point but maybe it is for aesthetics.

[markc]

The Architect ?

[flanagaj]

Sorry.  TA (technical architect)

[Nickfromwales]

Parapet looks better than an upstand?! And far more robust for directing runoff, also hides the slope.

 

Is this really a bank breaker? Not a lot of insulation here, and if I was going to pay to install poor insulation or the same labour / time to fit much better insulation…..🤔

[flanagaj]

9 minutes ago, Nickfromwales said:

Parapet looks better than an upstand?! And far more robust for directing runoff, also hides the slope.

 

Is this really a bank breaker? Not a lot of insulation here, and if I was going to pay to install poor insulation or the same labour / time to fit much better insulation…..🤔

That's a fair point.

[saveasteading]

Its certainly very well insulated. Lucky car. What is the garage door spec? Is it insulated? What draught seals are around it?

If not a very special garage door then your heat will pour out of it and all the extensive  insulation will be pointless.

 

It's designed to a house spec. Either that is all your designer does, or you intend  slowly turning it into a habitable room which I can't condone.

[Tony L]

34 minutes ago, saveasteading said:

 What is the garage door spec? Is it insulated? What draught seals are around it?

 

 

These were my first thoughts.  If you've identified an affordable, reasonably airtight garage door, I'd be interested to hear about it, please.

[Nickfromwales]

42 minutes ago, saveasteading said:

Lucky car

 

3 hours ago, flanagaj said:

The garage will be my workshop and gym so having something that is not Baltic during the winter months is the main criteria

👆👌

[Nickfromwales]

5 minutes ago, Tony L said:

 

These were my first thoughts.  If you've identified an affordable, reasonably airtight garage door, I'd be interested to hear about it, please.

The other thing to remember is, that if air can’t travel through this ‘room’ then the door can just be insulated and ‘draught-proof’ as best as you can get, with no need for it to be airtight (nor will you find one).

 

You’ll find that you can just use a small fan heater which will keep it super comfortable; my less than excellently draught proofed man-shed is fine without any insulation, with 2x 1kw fan heaters if one won’t cut it, but this will be bucketloads better.

 

Just have a draught excluder type doo-dah on the bottom of the door, and have that seal to the ground as best as you can.

[Tony L]

3 minutes ago, Nickfromwales said:

The other thing to remember is, that if air can’t travel through this ‘room’ then the door can just be insulated and ‘draught-proof’ as best as you can get, with no need for it to be airtight (nor will you find one).

 

 

I don't want my garage to be completely airtight, but I was thinking, if it was a lot more airtight than most garages then I could run a PIV in there to pressurise the room & dry out the cars when they need it - some of my cars are old & may be left for weeks at a time without being used.  Also, I might heat the garage if I'm working on one of the cars during the winter.  I have the PIV that was rescued from my bungalow before it was demolished.

 

I'm thinking the best solution may be to have a regular garage door, for security, then some king of curtain arrangement inside to increase the air tightness.

[markc]

I have just bought a Teckentrup insulated door and it looks good quality, not fitted yet but will be in a couple of weeks.

[Iceverge]

Why not use insulated metal panels? 

 

You could reduce the amount of ceiling timbers then too. 

[saveasteading]

I'm renovating a pitched small farm shed, 12m x 9m, to be a garage, store, workshop. We are putting 40mm composite on the roof and walls, nothing on the floor.

The doors may be up and over , with virtually no insulation, or perhaps a wooden pair, a little better.

Heating will likely be infra red pointing at work bench.

It won't be Baltic.

 

5 hours ago, flanagaj said:

garage will be my workshop and gym so

Not a garage at all then? No car type door?

I suggest you design it for that, including any PP and building regs it needs. 

Otherwise the insulation and ufh are  wildly excessive. 

Lose the parapet and fit external gutters and this will reduce risk long term, and make construction easier and insulation better. You can add a rainwater barrel for car cleaning nearby.

All in all, there's  a good few £k saving.

[Nickfromwales]

If I had the chance UFH would be 100% going in my garage / place to hide away and tinker.

 

Defo on the hitlist if I ever build, eventually, maybe, possibly.

[flanagaj]

58 minutes ago, Nickfromwales said:

If I had the chance UFH would be 100% going in my garage / place to hide away and tinker.

Given the cost of adding a UFH loop into the slab is going to minimal in the grand scheme of things, I think that is what I am going to do.  Will be a perfect man cave for tinkering away during the dark and dreary 5 months of the year.

[Nickfromwales]

59 minutes ago, flanagaj said:

Given the cost of adding a UFH loop into the slab is going to minimal in the grand scheme of things, I think that is what I am going to do.  Will be a perfect man cave for tinkering away during the dark and dreary 5 months of the year.

I’m in complete agreement. 
 

Don’t cave in to the nay-sayers, they can have what they want in their build, you have what you want in yours.

 

Id have UFH under my bbq patio if I’d have thought about it soon enough lol. 

[LnP]

Should there be a cavity tray below the coping in the parapet?

[Iceverge]

I would do full fill mineral wool batts in the cavity.

 

Not PIR boards. It's impossible to do them right.

[Nickfromwales]

11 hours ago, Iceverge said:

I would do full fill mineral wool batts in the cavity.

 

Not PIR boards. It's impossible to do them right.

Nothings impossible  
 

Well, I’m a bit dubious about the guy in a dress feeding 5000 people with 2 sardines and a demi-baguette…….  

 

I’d set each board in with a line of 330 foam to stop airflow behind them, and probably do the first really good job of fitting rigid insulation batts that’s ever been done.
 

Agree though, super wall 32 etc is the best method here for sure as it stops the majority of airflow too.

[flanagaj]

I am glad that the point regarding batts vs PIR insulation has been raised.  I have just calculated that I need 252m2 of insulation.  If I cost this up for 90mm T&G PIR, it's an eye watering ? 5.7k (£22.50 / m2) which is about 3k more than cavity batts.  The architect has done the drawings with a 150mm cavity which will means that we could in theory go 140mm cavity batts?

Our property is not sitting high on a hill and is not very exposed to the elements.  The top part of the house is also timber clad.

Unless there is any real benefit to having PIR, I am considering changing to 140mm with a 10mm gap, or would people just suggest go full fill?

[Iceverge]

Full fill or EPS blown beads. 

 

EVERY

 

SINGLE

 

TIME 

[flanagaj]

5 minutes ago, Iceverge said:

Full fill or EPS blown beads. 

 

EVERY

 

SINGLE

 

TIME 

I'm not disputing, but can you explain your reasoning?  My only reservation (I am a Luddite), is that a cavity is meant to breath and a cavity that is fully filled cannot?

[Iceverge]

Partial fill is impractical to do correctly. 

 

The beads or the mineral wool batts are good at keeping any water that gets in outside to the external leaf. Blown mineral wool is different, not encouraged with brickwork. 

 

In Ireland we have been full filling with EPS beads with 20 years and this place resembles a jetwash for 9 months of the year. The only failures I have heard of are from bad window and cavity tray detailing etc. 

 

 

 

[Mr Punter]

7 minutes ago, Iceverge said:

Full fill or EPS blown beads. 

 

EVERY

 

SINGLE

 

TIME 

 

I notice that BBA have withdrawn their certificates for EcoBead and Thermobead and replaced them with versions that are more circumspect regarding behaviour in relation to fire.  I imagine this is the case with all blown poly bead products.