Devon TRF Group Forum

devondan · Champion

Insulating my garage

Jerry atterick · Expert

For what it is worth:
Ive got old farm barn buildings let out as workshops.
We had a real bad case of condensation dropping from box profile, poured in.
We used cheapest 50mm polystyrene from "Minster Insulation", Marsh Barton.
If you batten off the underside, ideally 10 -12mm, making sure you run top to bottom, then 50mm polystyrene and then fix back into the line of the spacer battens.
ie 12mm air gap.
The condensation is hugely reduced due to far less temperature differential, the air gap allows what develops to evaporate and in the unlikely event that a drop of water does fall, then it will just run down the insulation.
It absolutely transformed my workshops.
Word of warning, birds absolutely love polystyrene!!!
Basically you get 80% of the benefit for 10% of the cost and no dripping ceiling!

devondan · Champion

I can't do that easily I'll have to batten the purlins to get air movement from the apex to the eaves (no eaves ventilation) and that will lower the ceiling to below the window height requiring some fancy timber work. Not a great fan of polystyrene that close to the action due to the fire risk!

RichT4 · Champion

How about just heating the bikes?

I am contemplating a similar thing. Was looking at mains powered 28W reptile heating mats, putting one under the sump of each bike and throwing over a large blanket.
That should provide a thermally stable micro environment to keep the bike warm & dry.

Could also just use a low power heat lamp or even just halogen house bulb.
You can get 18 & 25W light bulbs, put it in an old used bean can with vents in it - done.
A low powered heater to place under your bike. You'd probably only need for a couple of months a year anyway.

-- Edited by RichT4 on Thursday 17th of November 2016 10:27:18 AM

cee-b · Clubman A

You've probably already considered this, but how about just improving the ventilation? A couple of airbricks could solve the condensation problem a lot easier (and cheaper) than trying to insulate & heat.

doug9270 · Powermonger!!

cee-b wrote:
You've probably already considered this, but how about just improving the ventilation? A couple of airbricks could solve the condensation problem a lot easier (and cheaper) than trying to insulate & heat.

I have a similar garage to dan and have some condensation when its very wet outside but this soon dissipates when the moisture levels drop, i agree with with the above comment, venting is the answer.

Hoops · Elite

Or a Bike Bubble! Looked at getting one for my ZZR, not taken the plunge yet.

lanesteg · Sportsman

Insulation nor heating will solve the problem on there own, to answer one of your questions though the vapour barrier would go on the warm side of the insulation. but as others have said, ventilation is your issue. position air brick to create a subtle flow of air though the garage and that should solve the problem.

RichT4 · Champion

The problem I have is that the garage stays cold, almost always cooler than the outside during the day. Early Spring I tend to work outside as it's warmer.

During Winter/Spring, as soon as warmer air enters the garage it forms condensation on everything metal.
I think subtle ventilation would only increase the amount of condensation. It'd need a lot of ventilation for the whole garage area, bikes & tools to follow the outside temperature more closely.
Hence why I think heating the things that you don't wanting condensation to form on could be an easier solution for the months it happens.

Or put your bike in a zip lock bag with some rice in there (Bike Bubble). wink

devondan · Champion

My situation is pretty much the same as Rich's. The garage does have reasonable ventilation aided by a badly fitting door!
But the condensation is on anything metal rather than from the structure. The bikes get cold then stay colder than the outside so much so that if I open the door and let in moist air (not helped by the nearby stream) the bikes get instantly wet. My problem with heating the things I don't want condensation on is I have too many! Particularly the spare engines etc on the shelves. I thought that by using a low wattage heating tube I might be able to keep everything avove the dew point, but I'd only be able to do that cheaply with more insulation. creating a cold roof might work but I like the headroom and it won't be easy because of the window height.

RichT4 · Champion

Plastic boxes Dan... you can get really big clear plastic boxes with tight fitting lids. Engines & engine spares can go in there along with a desiccant.
We are in the process of plastic boxing everything that lives in our large garden shed, including my bike gear.... as the last thing I want is a mouldy helmet.

We bought about 10 of these, the delivery driver was really happy that his van was almost completely filled with our one order. wink

There are all shapes & sizes so I'm sure you'd find one to fit.

Then you've just got the bikes to worry about.

NickJ · Clubman A

I did my garage roof with this stuff HERE.

Easily fixed by staples and has been surprisingly effective, so about to do the walls now.

My damp problem was coming up through the concrete floor, but fixed with a good sealant.

gaschef · Devon's Best

Dan Screw some 2 X 2 timber to the roof ply and then cover over with some foil backed plaster board or some thin ply. You then have a two inch insulating air gap between the roof and the inner lining. Some one inch holes cut at intervals cut at the bottom and up near the ridge will give the air space some ventilation. You could also try Thompsons water shield painted on the block work you would be surprised how much moisture comes through what appears to be dry walls.

devondan · Champion

RichT4 wrote:
Plastic boxes Dan... you can get really big clear plastic boxes with tight fitting lids. Engines & engine spares can go in there along with a desiccant.
We are in the process of plastic boxing everything that lives in our large garden shed, including my bike gear.... as the last thing I want is a mouldy helmet.

We bought about 10 of these, the delivery driver was really happy that his van was almost completely filled with our one order.
There are all shapes & sizes so I'm sure you'd find one to fit.
Then you've just got the bikes to worry about.

Yep and about as much as cost of the celotex, mind you it might come to that!

devondan · Champion

gaschef wrote:
Dan Screw some 2 X 2 timber to the roof ply and then cover over with some foil backed plaster board or some thin ply. You then have a two inch insulating air gap between the roof and the inner lining. Some one inch holes cut at intervals cut at the bottom and up near the ridge will give the air space some ventilation. You could also try Thompsons water shield painted on the block work you would be surprised how much moisture comes through what appears to be dry walls.

I did think about that but the purlins get in the way so I'd need holes at the bottom, Two sets at the middle and another at the top, and I'd be worried it would let the warmer moist air get to the cold ply under the shingles, or am just over thinking everything as usual!

-- Edited by devondan on Thursday 17th of November 2016 07:35:20 PM

-- Edited by devondan on Thursday 17th of November 2016 07:36:16 PM

russell11031967 · Devon's Best

Celox is great but you must leave an air gap above it , minimum of 25mm, tyvek is no good as a vapour barrier as it is breathable, use a thin gauge polythene on the underside of the celotex. the air gap above the celotex needs to be vented at the eaves .

Devon_Rich · Clubman A

Worth having a look at seconds and co. They sell kingspan factory rejects. Used a few years ago... not sure what they are like now

devondan · Champion

russell11031967 wrote:
Celox is great but you must leave an air gap above it , minimum of 25mm, tyvek is no good as a vapour barrier as it is breathable, use a thin gauge polythene on the underside of the celotex. the air gap above the celotex needs to be vented at the eaves .

There is no way to vent at the eaves the ply screws straight to the wall plate, there's no place for any holes that wouldn't let water in!

potus · Clubman A

devondan wrote:
gaschef wrote:
Dan Screw some 2 X 2 timber to the roof ply and then cover over with some foil backed plaster board or some thin ply. You then have a two inch insulating air gap between the roof and the inner lining. Some one inch holes cut at intervals cut at the bottom and up near the ridge will give the air space some ventilation. You could also try Thompsons water shield painted on the block work you would be surprised how much moisture comes through what appears to be dry walls.

I did think about that but the purlins get in the way so I'd need holes at the bottom, Two sets at the middle and another at the top, and I'd be worried it would let the warmer moist air get to the cold ply under the shingles, or am just over thinking everything as usual!

-- Edited by devondan on Thursday 17th of November 2016 07:35:20 PM

-- Edited by devondan on Thursday 17th of November 2016 07:36:16 PM

I'd agree with your view Dan, the 'warmer' air would enter the holes and would likely condense on the cold ply surface pretty much as it is now. The air gap would really need to be separated from the internal and external air to provide any insulating properties.

I'd personally put up some insulation board and foil lined plasterboard.

devondan · Champion

Would you put a gap between the insulation and the ply? I.e. fix it on top of the purlins? Or put the insulation against the ply so there is no space for condensation? Note that there is no condensation on the roof at the moment only on the bikes.

russell11031967 · Devon's Best

devondan wrote:
russell11031967 wrote:
Celox is great but you must leave an air gap above it , minimum of 25mm, tyvek is no good as a vapour barrier as it is breathable, use a thin gauge polythene on the underside of the celotex. the air gap above the celotex needs to be vented at the eaves .
There is no way to vent at the eaves the ply screws straight to the wall plate, there's no place for any holes that wouldn't let water in!

could you vent from the verge/gable end ? is there a soffit of barge board running up the gablend? you could cut vents into Cross venting is not as effective as up and over but if you could vent both sides and ends it wouldn't pass building regs but sure it would still work smile

potus · Clubman A

I'd put the celotex up against the wood

Used to do thermal resistance and interstitial condensation calcs all the time, rarely need to do them nowadays and I'd use software now anyways.

The insulation of the roof will certainly help reduce the heat loss from the garage.

russell11031967 · Devon's Best

potus wrote:
I'd put the celotex up against the wood

Used to do thermal resistance and interstitial condensation calcs all the time, rarely need to do them nowadays and I'd use software now anyways.

The insulation of the roof will certainly help reduce the heat loss from the garage.

As I said before the Celotex needs an air gap between it and the timber above ( standard building practice) BUT THAT VOID NEEDS VENTILATION but what do I know I only build houses confuse confuse wink

wackyracer · Powermonger!!

mine works perfect

Celotex is king especially free stuff wink

Jerry atterick · Expert

Basically everyone is on the same wavelength, polystyrene, celotex or microfoil but most importantly air gap and vented.
All of which are inflammable, possibly not the air - tee hee!
Maybe an extra fire extinguisher, if the insulation has caught fire in the roof then you are f******d anyway?
The only solution that covers that is plasterboard, ie normal set up!
Not being funny but why on earth didnt you sort the insulation when the roof was off?
That way no cutting in, full sheets, long fixings, batten off for tyvec and air gap then screw down roof covering.
Thats how I improved our utility roof, all to building regs.
You need an air gap, if you dont seal off the inside of the workshop with any of the above, then it will be drafty, but wont drip so much.
Its a man cave - it has to be right!

RichT4 · Champion

It's interesting to read all these methods but what are you/we all trying to achieve?

Insulation or ventilation?

Ventilation of the insulation is needed I guess, to stop the insulation becoming a damp trap and breeding mould.

Ventilation of the work area is not desirable as it bleeds the warmth out and will inject fresh warmer humid air in, which will condense on colder surfaces.

We've already established (in Dan's case) that moisture is not coming in through the floor, walls or ceiling. It comes in via the air and mostly once the door it opened, the only way to protect against this is to ensure that the contents are warm enough to prevent condensation forming.

I guess the air in the garage/workshop space needs to be trapped in pretty well (when not in use) so the low wattage heaters, in conjunction with all the improved insulation can hold the room at just above outside temperature. So is the solution actually to insulate and then seal up the room?

devondan · Champion

The ventilation thing isn't clear cut, it used to be the case that flat roofs were ventilated above the insulation, but that's not recommended now. If you look at American houses where they use shingles the insulation is below the boarding although it is above the rafters. I could batten off the purlins and put celotex on that but it would only be vented at the ridge unless I put some kind of vent on the roof slope. I suppose I am looking for reassurance from someone else who has put the insulation against the boarding and sealed it and had no problems! I know a vented space would be best but you have to look at the picture and suggest the best way to achieve it!
Why didn't I do it when I re roofed? Good question but I have 3 sheds all were covered in deteriorating asbestos l didn't have enough money to re roof them all, insulate them and pay to dump the asbestos! Plus I didn't know I had the problem at the time!

-- Edited by devondan on Friday 18th of November 2016 09:26:26 AM

-- Edited by devondan on Friday 18th of November 2016 09:29:28 AM

devondan · Champion

Rich.
Yes heating and sealing will do it. If I can keep the air warm enough to keep the bikes above the external air dew point temp I shouldn't get condensation on them when I open the door. The insulation is to reduce the heating cost. I have a screwfix fan heater which warms it up quickly if I'm working in there but it's 2kw, which would be a tad expensive to leave on 24/7. But by warming the air I'll be increasing the moisture being held by it an therefore increasing the risk of condensation on the roof. That's the conundrum!

RichT4 · Champion

ah, I'm with you.

potus · Clubman A

An interesting read....

www.superhomes.org.uk/resources/insulate-a-flat-roof/

Jerry atterick · Expert

We are a sad lot - tee hee.
Made me smile watching this thread, we all need a nice warm shed, music of our choice, place for coffee, plenty of bike, nice old cumfy armchair (if room), good mates (if more than one!) and a bleddy good giggle.
Tiz wot life is all about!!!!!!

devondan · Champion

Trouble was .... I'd had to take the juke box out of the garage as it was getting damp!

I think I have a plan. I'm going out to the garage with a beer and think some more!!!

providing I can sort the windows, putting battens on the purlins might be the earliest way, might even do a mock up!

RichT4 · Champion

Wow Dan, must be getting you down if you're drinking this early in the morning! wink

Jerry atterick · Expert

Ive got plenty of new free batten, if that helps, Tedburn.

devondan · Champion

Jerry atterick wrote:
Ive got plenty of new free batten, if that helps, Tedburn.

Might take you up on that, I'll be needing about 24!

Andyxt · Clubman B

devondan wrote:
Trouble was .... I'd had to take the juke box out of the garage as it was getting damp!

....

Curious about which box you've got in there?

I have an Americana - no room for it in the garage though that's where I'd like it!

Jerry atterick · Expert

Jealous!

devondan · Champion

It's a ro ami disco 200, needs a bit of tlc but is all working!

Lost · Expert

Hi Dan for what it's worth as they say I have a oil heater in the bunker its electric operated and fixed to the roof / ceiling