Removal of gas fireplace flue and increased condensation

[JayN]

I was scratching my head why suddenly there is condensation on the windows in the mornings, I couldn't remember having changed any of my habits and always when I switch on the central heating around October windows stay clear and dry fro then on. Even some black dots started appearing on the ceiling above couple of windows.

Well, I did take off the gas fireplace's (which I've never used) flue below to the roof level when I installed the dry ridge and swapped a few roof tiles in the summer. Absent mindedly I also placed a piece of timber or plaster board on top of the flue opening up in the loft, daft idea being if a small animal gets inside it can't get down into the living room...

I've always felt that the loft is very well ventilated, there's always a nice wind up there, so my plan is to just open the flue into the loft space put some mesh on top, ventilate into the loft space and place a few of those plastic underlay spreaders near the flue. I'll then check a few times in the winter if there is condensation in the loft and if there is I'll install a few of those vented roof tile that match Marley moderns. There are alredy quite a few of those round soffit vents.

How's that for a plan? Any better ways to solve the problem? Thank you.

 

[JayN]

Yep, I'd put a plastic cover and some weight on top, the underside was dripping wet, moisture trying to escape.

Undersarking has been fitted quite loosely, so probably didn't need to order the plastic thingies, nice fresh wind blowing as I remembered.

You just can't beat a 1970 bungalow, it's a brilliant design for people to whom the idea of paying for scaffolding is repulsive.

 

[ree]

OP,
Your flue should be swept, even tho the stack has been taken below roof plane & terminated in the loft. Ventilation is necessary at the bottom of the flue & at the top. Do you only have the one fireplace in the bungalow?

The classic, but disagreeable to some, response to condensation is trickle heat and trickle ventilation.

 

[^woody^]

You should not vent air from the house into a roof void. That warm air will condense in there

If you have altered the equilibrium of the internal environment by altering ventilation via a flue, then that could be a cause of internal congestion.

 

[Si_]

I had the chimney removed below roof level when I had a reroof. Covered the flue opening with a cloth. Left some slight ventilation behind the skirting board - a few mm where the fireplace used to be - and installed an extractor fan in the gable end that I can set to trigger by temperature or manually from my phone. Although humidity has never gone above 65% in the room or 80% in the loft, as yet.

 

[^woody^]

It's no good measuring RH alone and trying to diagnose. There can be wide variations with no issues.

If you are suddenly getting excess room condensation, then you need to investigate what's changed. We are currently in condensation season with the change of season, but if historically you have not experienced condensation issues at seasonal change, then looking at structural or lifestyle changes would be the thing to do.

 

[JayN]

Three mornings now without any condensation on any of the windows, not a drop. Today I installed those plastic undersarking separators and everything was dry as a whistle. I could actually feel a cool breeze on my face - that's how good the ventilation is there so I am not too worried yet about ventilating into the loft space.

I'll monitor the situation though every couple of weeks and especially when we get some colder weather.

It's uncanny really. The bedrooms are far away from the fireplace, behind corners and a long narrow corridor and still the opening of the flue worked, and immediately.