garage floor Insulation Question

[GlennSpray68]

HI all ,
I hope someone can help with my dilema ?
I am wanting to batten out and insulate my single storey single brick skin attached garage ,the house is a 1960's semi. for use as a gym/ utility room, not a habitable conversion
I have a couple of questions regarding the insulation aspect .
the garage is 7ft wide by 24 ft long

1. The garage floor slopes severely with a fall of about 8 inches from the centre point halfway towards the old garage door which has been replaced with double glazed units and french doors. the floor is a solid concrete type , but i can see no sign of a dpm . the house has a black plastic dpc about 2 courses up from the level centre point of the garage .

The problem I have is that the dg doors are flush to the concrete floor so i cannot put in a joist floor to level this off as this would mean the floor level would be about 8 inches up at the french doors .


My question is I have about 1" at the doors so I thought about putting in a dpm then covering this with Airtec Double Insulation foil which is thin , fasten 2X1's to this with 25mm kingspan in between the lats then putting 3/4" ply on top . this will still give the garage a slope but hopefully will provide better insulation . Is this feasible

also with regard to the roof insulation . The roof is a cold roof with exposed 3X2 joists , if I leave a 25mm gap next to the top for air venting then put in 50 mm kingspan in there and finish off with foiled backed plasterboard , will I be able to vent the air gap into the garage space or does it have to vent externally which would be very difficult to achieve ?

I hope someone can help with the floor problem in particular as its doing my head in how to sort it .

Many thanks in advance for any help as it will be greatly appreciated .

Glenn

 

[KingspanInsulation]

GlennSpray68
Thanks for posting your questions

Regarding your floor query, while the foil insulation you have specified is not one of our products a little research seems to point out that this is an insulation for use in a suspended timber floor. A suspended timber floor is one where the floor joists are suspended above the ground to allow air from the outside to run below them. As the floor type that you are suggesting is not a suspended floor I would suggest that this foil layer is not required.
With any concrete floor where you are unsure if DPM is present it would be good building practice to add a new one, many different types are available and we would not recommend any more than another. Your timber battens could be fixed through the DPM into the concrete and the Kingspan Insulation laid between the battens. We would suggest that Thermafloor TF70 is ideal for this application. Over the battens and the insulation we recommend a polythene sheet (500 Gauge is fine) is laid before laying the ply on top. http://www.kingspaninsulation.co.uk.../Thermafloor-TF70.aspx?disposition=attachment see page 4 and page 9 for guidance

Your roof query is unfortunately governed by Building Regulations and British Standard. Both say that where you are creating a 'cold roof' construction a minimum 50mm ventilated airspace should be maintained between the underside of your deck and your insulation. This should be allowed to ventilate from the outside - to the outside. Venting into the room would simply be allowing hot/cold air past the insulation which would rather defeat the object of insulating in the first instance. So, if you maintain the depth of your joists you would only be able to get 25mm between your joists safely.

I hope this helps

 

[tony1851]

I thought about putting in a dpm then covering this with Airtec Double Insulation foil which is thin ,

However you insulate your floor, don't waste time with foils. They are a con and a complete waste of money. What little insulation value they have is obtained via the reflective foil, which will only work when it faces an un-vented cavity; putting anything directy against it therefore defeats the object. You would get the same result at lower cost by using kitchen foil from Tesco.

 

[GlennSpray68]

Thanks very much for your responses it has helped a great deal

Glenn