condensation in shed/office

[lampygreg]

Hi, wondering if anyone here has some expertise in building that can suggest a good solution for me. I have built a 16' by 10' outbuilding at the end of my garden. Effectively it's a glorified shed, it is timber construction with a slightly sloped shed style roof, there is a patio door installed. As it was built as an outside office for my girlfriend who works from home i have gone crazy on the insulation, i lined the inside of the outer walls and ceiling with a double foil lined bubble wrap material then 100mm celotex boards inside the walls and ceiling then 8mm ply boards for the internal walls. As you would imagine it's great at holding in warmth. However now i am getting really bad condesnation inside, i understand that i need to get the moist air out and was thinking maybe i could install an electric extractor fan at the highest point inside. Was thinking perhaps an Xpelair LV100H it's a extractor with an inbuilt humidity sensor. One question would be, would i need airflow coming in to the building from another point ie down at the bottom like an air brick also. Obviously my biggest fear is to lose all the heat i've worked so hard to keep inside. Any suggestions? Thanks

 

[Newboy]

How are you heating the shed/office?

 

[theprinceofdarkness]

An inlet air brick will result in the air moving directly from inlet to outlet. I have actually seen this in a smoke test on an industrial building. Though it is better then nothing.
There are specs for the number of air changes per hour for various types of room usage, the trouble is that a fan will only move its amount of air if it has free air being fed to it. So I would find out the air movement required for light clerical duties and get a substantially higher rated fan, so it will try to suck air in via any leaks, so have a better distribution of air flow. If it runs more or less all the time, then a small air vent (like a soffit vent) might be enough.?
Condensation occurs mainly when the air temperature falls to less then 10-12%.
What does it do if the outside humidity is 80% and its warm outside ?
Frank

 

[lampygreg]

Hi frank, you seem like exactly the kind of knowledgeable person i need right now.
We are using an electic oil heater at the moment, due to the amount of insulation this is great at getting the room warm and keeping it warm.

here are some images to show the build as i went.

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• lampygreg
• 21 Jan 2015
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• lampygreg
• 21 Jan 2015
• 1

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• lampygreg
• 21 Jan 2015
• 1

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• lampygreg
• 21 Jan 2015
• 1

Thanks for looking

 

[lampygreg]

Hi, looking at the pictures it's pretty easy to see why i have condensation.
Where would you recommend i fit vents or airbricks? One top one bottom. Both at top?

 

[lbzbean]

I wonder if you could find a used MHRV on eBay or something, that would give you ventilation without loosing your heat?