MHVR reduce damp?

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Tommy91

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I’ve recently moved into a 1940s bungalow and there’s a damp issue in most rooms. As it’s recently became colder over the last month, the damp has increased significantly.

I’ve been looking at MHVRs as I think one of the main issues I have in the property is that the ventilation in the property isn’t great.

Does an MHVR system generally reduce dampness / humidity?
 
Most 'damp' issues aren't actually caused by damp, it tends to be caused by condensation and the main cause is lack of airflow. Positive or forced ventilation works well to rectify this. They came into fashion quite a few years back and then seemed to fade out, but an electrician I work with is currently fitting at least two a week and he's getting very positive feedback. The system does seem to work.
 
Tommy91 said:
I’ve recently moved into a 1940s bungalow and there’s a damp issue in most rooms. As it’s recently became colder over the last month, the damp has increased significantly.

I’ve been looking at MHVRs as I think one of the main issues I have in the property is that the ventilation in the property isn’t great.

Does an MHVR system generally reduce dampness / humidity?
Click to expand...
INSULATE!
With all the vents and the will in the world, you wont make a significant difference until you insulate the outside walls, to a decent standard.
 
Do both; insulation reduces your paid-for heat getting lost through the walls/roof/floor and MVHR reduces your paid-for heat being lost through the air.

Also, embark on a serious and careful sealing up of every gap in the fabric of the building to eliminate draughts; you're installing controlled ventilation, don't leave anywhere that is performing uncontrolled ventilation, especially if it means cold world air can reach the room side of insulation.

Finally, examine your lifestyle regards moisture generation. Boiling stuff every cooking session, having 200 cups of tea a day and exclusively drying washing on radiators all adds to the moisture load in the air that the house has to deal with. An MVHR will condense it out but running elevated humidity in a house is still a good way to foster ill health and insulting all your rads by throwing clothing on them doesn't help your heating system perform its job
 
A cheap short term solution is a dehumdifier.
You could be emptying it up to two times a day, with about 2 litres each time, so if you can get one that can drain to somewhere (e.g. a shower tray) it'll save you faffing about emptying it.
It might give you a good idea of the potential effectiveness of the MHVR in reducing air-borne moisture.
 
Dehumidifier will be more effective if you can get the internal wall surface temperatures to 14 degrees C. Below this, condensation on walls is still likely. Whether or not your deh has a continuous drain I find it to be more effective to drill a hole in the side of the water tank, high up, then pass a flexible hose with an outer diameter 1mm larger than the hole, through the hole and down into the bottom of the tank. As the tank fills eventually a siphon will start and empty the tank. The siphon flow rate will be higher than a continuous drip drain and will help keep the pipe clear. I find with drip drained dehs the pipe eventually gums up with slime
 
noseall said:
INSULATE!
With all the vents and the will in the world, you wont make a significant difference until you insulate the outside walls, to a decent standard.
Click to expand...
As in like cavity wall insulation?
 
robinbanks said:
Do both; insulation reduces your paid-for heat getting lost through the walls/roof/floor and MVHR reduces your paid-for heat being lost through the air.

Also, embark on a serious and careful sealing up of every gap in the fabric of the building to eliminate draughts; you're installing controlled ventilation, don't leave anywhere that is performing uncontrolled ventilation, especially if it means cold world air can reach the room side of insulation.

Finally, examine your lifestyle regards moisture generation. Boiling stuff every cooking session, having 200 cups of tea a day and exclusively drying washing on radiators all adds to the moisture load in the air that the house has to deal with. An MVHR will condense it out but running elevated humidity in a house is still a good way to foster ill health and insulting all your rads by throwing clothing on them doesn't help your heating system perform its job
Click to expand...
Yeah we don’t do any of that. Majority of things are dried outside and have maybe one coffee a day, so I think the lifestyle is fine.

Maybe replacing the windows could help
 
robinbanks said:
Dehumidifier will be more effective if you can get the internal wall surface temperatures to 14 degrees C. Below this, condensation on walls is still likely. Whether or not your deh has a continuous drain I find it to be more effective to drill a hole in the side of the water tank, high up, then pass a flexible hose with an outer diameter 1mm larger than the hole, through the hole and down into the bottom of the tank. As the tank fills eventually a siphon will start and empty the tank. The siphon flow rate will be higher than a continuous drip drain and will help keep the pipe clear. I find with drip drained dehs the pipe eventually gums up with slime
Click to expand...
Would you recommend your dehumidifier?
 
Tommy91 said:
As in like cavity wall insulation?
Click to expand...
Not really. CWI is typically 100mm or less of a woolly type of insulation, about half or less what modern regs demand, performance wise

Tommy91 said:
Maybe replacing the windows could help
Click to expand...
It all helps. You can go all the way to not needing a heating system at all if you like

Tommy91 said:
Would you recommend your dehumidifier?
Click to expand...
I've no complaints with it, but it runs in a storage room, not the house.. the house has a Vent Axia Sentinel Kinetic Plus B
 
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robinbanks said:
Not really. CWI is typically 100mm or less of a woolly type of insulation, about half or less what modern regs demand, performance wise


It all helps. You can go all the way to not needing a heating system at all if you like


I've no complaints with it, but it runs in a storage room, not the house.. the house has a Vent Axia Sentinel Kinetic Plus B
Click to expand...
Thanks for the explanation. What insulation would you recommend?

If you don’t mind me asking, how much was the vent axia MHVR you mentioned?
 
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