Garden office too hot

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jonnypron

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Thames Ditton
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I've built a garden office last year and is well insulated, breathable membrane, air gap then cladding for breathable aspects. On the warm side i.e. before internal walls is vapour barrier which I research as the best for stopping moisture in winter, and effectively creating a sealed box.

The problem I have is it's baking hot in summer. I have a large fixed window, and glass door. Semi UV glass, but still radiates a lot of heat. Celotex in the ceiling and floor and rock wool in the walls. I thought this might stop a certain amount of heat build up, but with the door open for air flow it's 30+degrees C by the end of the day I lock up and the heat creeps up to 34/35 degrees and is like a sauna. I was wondering if air vents would help (one front and one back) but also concerned after all I read about ensuring the vapour barrier is sealed everywhere, how will this be affected when adding two large holes?

Thanks
 
Can you get a window or similar in the roof ? I keep upstairs windows open & it creates a flow of air through the house. Or some solar panels powering an air con unit? The problem is hot weather is not a prolonged problem in this country so you could be spending lots to solve a very limited problem.Or an indoor water feature, if space allows.
 
Grow a tree over it for shade, or a solar shade?

Can't advise on whether the vents would compromise the build, but i can't see any vents offering much succour, with the weather like this.
 
jonnypron said:
door open for air flow it's 30+degrees C by the end of the day
Click to expand...

But its nearly 30 degrees outside today -insulation wont get the inside cooler than the outside!

What is happening is that the room when all closed starts at the ambient temperature, but the glazed doors and windows allow solar gain hence why it heats up. then you open the window to get it to cool down, but the lowest you can achieve is the external temperature + a bit more where the air doesnt circulate.

Air con is your friend!
 
Notch7 said:
But its nearly 30 degrees outside today
Click to expand...

upload_2018-6-27_16-35-33.png
 
A through flow of air using vents an opening window or even a second door will reduce the temperature or at least make it more bearable.

Open it as early as you can in the morning to encourage heat loss in the meantime

Blup
 
airflow over you skin makes you feel colder (due to sweat evaporation)

but does not reduce the temperature

In hot countries you have to shut the doors and windows as the sun starts to rise, and keep them shut. This concept is alien to Brits.
 
Interesting. Ive just been in our summerhouse built from 4inch concrete blocks and with 25mm polystyrene insulation in front and behind the wall and it is ice cold. Can you describe the layers of the building from outside going inwards?

Mine is dark brown stained shiplap cladding. 25mm insulation, membrane, 100mm blocks, 25mm insulation then 9.5mm plasterboard
 
Notch7 said:
But its nearly 30 degrees outside today -insulation wont get the inside cooler than the outside!

What is happening is that the room when all closed starts at the ambient temperature, but the glazed doors and windows allow solar gain hence why it heats up. then you open the window to get it to cool down, but the lowest you can achieve is the external temperature + a bit more where the air doesnt circulate.

Air con is your friend!
Click to expand...

I understand that in the day it's likely to be the same as outside, but it's when the day starts cooling down early evening that the room gets hotter and hotter as I have to lock up and close the doors. Could be the heat behind the solar blind or some electrical appliances e.g. computer, but it's weird the way it stays hotter in there than outside when evening hits. I often go in to open the door when it's dark and it's like 33/34 degrees c! not sure if vents will help it cool down in the latter part of the day when it's cooler outside and the sun is not on it anymore?
 
Brigadier said:
Grow a tree over it for shade, or a solar shade?

Can't advise on whether the vents would compromise the build, but i can't see any vents offering much succour, with the weather like this.
Click to expand...

Grow a tree over it... if I have 10 years + that would work! I have ordered a shade for the patio infront so will see how that helps as it'll cover the large window and door. (good word; 'succour')
 
nuzuki said:
Interesting. Ive just been in our summerhouse built from 4inch concrete blocks and with 25mm polystyrene insulation in front and behind the wall and it is ice cold. Can you describe the layers of the building from outside going inwards?

Mine is dark brown stained shiplap cladding. 25mm insulation, membrane, 100mm blocks, 25mm insulation then 9.5mm plasterboard
Click to expand...
hi, yes it's ;

WALLS: cedar cladding (on battens for air flow), breathable membrane, 100mm rock wool in stud wall, vapour barrier, then 11mm OSB.
CEILING: EPDM rubber roof, OSB, air gap, 75mm celotex in-between joists, no vapour barrier but foil tape over joins for celotex, OSB ceiling inside

 
How about just investing in a pair of shorts?

And given the unpredictability of the English climate, next year it's possible you'll be needing thermals!
 
forced ventilation (fans inward on the shaded side, outwards at ceiling height) during the night will cool it. However if it is made of wood and insulation it will not have much thermal mass, so will heat up quickly when the sun comes out.

Maybe you can fabricate shades for the windows.
 
Air moving over a surface will cool that surface. A well insulated building with air circulating through it WILL be cooler than that outside. A windowless extension I am building at the moment is several degrees colder inside than the outside. There is a marked difference.
 
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