A lot of moisture in insulated outbuilding

[mderoy]

I went to help a friend of mine wire up some network Ethernet ports to an outbuilding office he recently had built. It was built with a really good foundation from what I could see. Dug deep and insulation added and concrete poured in. The walls are those grey aerated blocks but sandwiched together with insulation in between. The roof is flat roof with insulation too. Exterior was rendered and painted. Windows and doors are double glazed and electric heating which heats to room quite well and heat retention is good doesn’t get cold quickly. Interior walls are dot and dabbed plasterboard. C

The problem is that he is having to run a dehumidifier constantly 24/7 regardless of usage and the container gets filled with water literally in about 6/7 hours. The window vents were closed so I told him to try keeping them open but it hasn’t helped.

Just wondering if anyone can shed any light on what could be wrong?

Thanks

 

[noseall]

I went to help a friend of mine wire up some network Ethernet ports to an outbuilding office he recently had built. It was built with a really good foundation from what I could see. Dug deep and insulation added and concrete poured in. The walls are those grey aerated blocks but sandwiched together with insulation in between. The roof is flat roof with insulation too. Exterior was rendered and painted. Windows and doors are double glazed and electric heating which heats to room quite well and heat retention is good doesn’t get cold quickly. Interior walls are dot and dabbed plasterboard. C

The problem is that he is having to run a dehumidifier constantly 24/7 regardless of usage and the container gets filled with water literally in about 6/7 hours. The window vents were closed so I told him to try keeping them open but it hasn’t helped.

Just wondering if anyone can shed any light on what could be wrong?

Thanks

Is this construction moisture, habitation moisture or recent weather conditions? He isn't running a gas heater in there is he?

 

[mderoy]

Is this construction moisture, habitation moisture or recent weather conditions? He isn't running a gas heater in there is he?

No there is no gas heater in there. It’s just purely electric heating. How do i know what kind of moisture it is? I mean weather has been cold lately but the moisture issue seems to still be same regardless of outside temperature. Maybe it’s construction moisture? It can’t be habitation moisture because it’s not being used at the moment and it’s collecting a lot of water in the dehumidifier.

 

[^woody^]

Likely still drying out if it has just been built.

Make sure the dehumidifier is suitable for the area involved, keep it on and close all vents. Wait until the amount of moisture being collected reduces

 

[mrrusty]

I agree that construction moisture is the most likely.

There is another consideration in that garden buildings get used infrequently. If allowed to get very cold, the blocks have a high thermal capacity, and will take a good while and fair bit of heat to warm up (Think storage heaters). If the weather has been close to freezing and all the block work is very cold, and then the weather suddenly changes to say 12 degrees and very high humidity (because it's raining), and if the outside warm humid air is let inside, the still very cold walls will see a fair bit of surface condensation until they warm up to the dew point of the outside air.

Insulation is about slowing down heat loss through a structure, but is not the same as thermal capacity which is about how much heat energy it takes to raise the temperature, or conversely how much heat energy the structure can store. You can have a material with very high insulation properties, but a very low thermal capacity which means it doesn't take much heat to raise the temperature of the structure. Condensation is caused by temperature differentials.

Unless you are going to regularly heat a garden room, you are better constructing it out of low thermal capacity materials like timber frames and SIPs rather than concrete brick/blocks, because they will adjust to the ambient temperature much faster, mitigating condensation risk.