Excessive condensation following Walls pumped

In the past few weeks I am getting enquiries about excessive condensation after walls have been pumped which was not there before. The installers have told the clients that they need to upgrade their heating systems, hence calling me! Upgrading the heating will not resolve this.

I have my theories on the causes but I would very much value some the excellent opinions from some of the posters here.

Main rooms that symptoms ocur are bedrooms. Excessive condensation is on windows but is leading to bad mould growth on reveals and ceilings. Have not looked at jobs yet but due to see one this week and one next week. Additonal vents have been installed but to no avail.

Shane007 said:

Additonal vents have been installed but to no avail.

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I would check to see if the vents are been left open and that they are not being closed by the clients to stop "draughts".

I would also check to see if radiators are been turned off by the clients in unused rooms to save fuel.

every situation is different, and this is my problem with the grants going to home-owner/contractor without an overview from an impartial experienced professional.

For instance, the cavity wall insulation may have reduced unregulated air-infiltration/ even reduced the breathability of the structure or caused more visible effects of thermal bridging.
but more likely this is due to a lack of ventilation and the ventilation that has been installed is not adequate in a more air-tight house. have a read of this particularly page 10 that deals with RH (granted its from a company, but it raises issues of retro-fitting without providing adequate ventilation.

all this does not mean we should not be insulating and sealing up our buildings to conserve energy. just that we must have an appropriate ventilation strategy

We were called to a house where condensation occurred in one of the bedrooms.
Young couple with a child - internal utility with dryer, vented to external, hubby liked to home cook - vented kitchen extract.

It was most prevalent at the window and at the floor.

We opened up the wall and found that the wall was insulated to the required standard of the time, but when we looked in the basement cr park we found that a 10M x 0.6M length of insulation was missing.
The insulation was taken to a line of column supports but not further, while the accommodation continued out beyond this point on that side of the building.
The adjoining apartment was empty and had no signs of condensation on the window.

There was no sign of water ingress through the structure - the cavity was bone dry as well as insulated and had a flashing tray correctly installed at the base.

The assessment was that

(i) the condensation came almost entirely from living processes, as opposed to washing and cooking
(ii) the metal framed windows were not thermally broken and contributed to condensation in the room
(iii) the north-facing micro climate meant that the required standard of insulation was borderline in its ability to cope
(iv) the absence of the under slab insulation pushed this combination of room orientation and cold bridging over the edge

Lessons learned -

Insulation
Orientation
Tracing Cold Bridging
Exclusion of obvious causes of water vapour in the air


ONQ

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.

lowCO2design said:

For instance, the cavity wall insulation may have reduced unregulated air-infiltration/ even reduced the breathability of the structure or caused more visible effects of thermal bridging.
but more likely this is due to a lack of ventilation and the ventilation that has been installed is not adequate in a more air-tight house. have a read of this particularly page 10 that deals with RH (granted its from a company, but it raises issues of retro-fitting without providing adequate ventilation.

Click to expand...

Yes this was more along the line that I was thinking. I have had 2 calls within last couple of weeks so I am wondering with the fall in temperatures, is this becoming a more common problem. Does cavity wall insulation hamper the natural breathability of a dwelling, in general terms of course?

lowCO2design said:

have a read of this particularly page 10 that deals with RH (granted its from a company, but it raises issues of retro-fitting without providing adequate ventilation.

Click to expand...

Interesting link - thanks.
I tend to assimilate things better with graphics than figures.

Interesting to see that bedrooms seem to have to deal with far higher rates of moisture generation.
I presume this is solely to do with sleeping occupancy transpiration/perspiration rates and closed windows.

Was the kitchen comparison taking into account the availability of rapid venting from windows and doors with less for bedrooms?


ONQ

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.

I don't know re kitchen comparison.. People do seem to appreciate the need to vent after cooking but do not seem aware of the amount of moisture created by themselves when sleeping

Following the step-by-step approach suggested above by ONQ and lowCO2 is definitely the way. I notice the same issue a few weeks ago and went through the list - found a broken vent and a few other issues that were affecting the condensation levels in the house. Also adjusted the temperature in the house so that we werent blasting the house out of it in the morning when the wall/window surfaces were coldest. Touch wood - seems to have done the trick for now.

lowCO2design said:

I don't know re kitchen comparison.. People do seem to appreciate the need to vent after cooking but do not seem aware of the amount of moisture created by themselves when sleeping

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It seems worse after the heat comes on the morning - with the room colder during the night (otherwise I couldn't sleep) there is little or no condensation.
Perhaps the warm air absorbs more and then transports it to the windows, which, being behind curtains are colder and therefore more liable to mist over.

Perhaps the heat coming on makes a person perspire/ respire more at the same time as the air gets warmer and can hold more water vapour.
It definitely seems to interrelated and the effect may be compounded by the windows being coldest just before the dawn/ end of the night.

That's another factor that should be watched - the time in the day when the condensation is at its worst.
Also the OP should check under floor coverings and behind wardrobes for damp/mould and fungal growth.
Spores can cause respiratory reactions in some people who may think they have a cold or flu.

ONQ

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.

were having a mild winter so far and there is a high RH as a result..

condensation is always going to form where the surface temp difference to the room temp is too great (i think you've posted the due point table before) (i use a rule of thumb of about 7deg difference) - so for a room generally at 20 you should have internal surface temp of greater than 13deg - this equates to (for instance) the installed u-value of window (taking in thermal bridging of ope etc) should be better than circa 1.2w/m2k

Interesting to read of that ball-park figure - 7 degrees difference.
I think I've posted *someone's* dew point table now that you mention it.
Having said that it's all bound up with the humidity, temperature difference aside.

I live on the north side of a hill and we regularly get a mist rolling over the top of it - the last two day have been particularly clammy.
We like to leave the windows open to "air" the place - the temperatures equalize and condensation is avoided plus we get multiple air changes per hour.
You can end up freezing your proverbials off, but a 20 minute stroll to the shops and back soon gets the circulation going - then you feel warm when you're back in front of the PC.

ONQ

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.

Warm air with a high vapour content moves through a house rising above the colder air.
It also tends to diffuse until a thermal and humidity equilibrium is reached.

Forced movement only occurs when you leave windows and doors open.
Such movement would tend to carry the vapour outside the house.

Its the process of venting we use daily to get rid of the vapour.
It might work as you suggest if it was prematurely stopped.

ONQ

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.

UPDATE: I visited the property in question and it seems like the beads have settled. The problem is only at high level on most external walls but also below the internal window cills! They have air vents in all rooms, however, they are installed upside down! They are the type has a covered inlet to catch rising air!!

I had a converastion with somebody sometime ago where they decided to fit some air vents in the walls a few years after the walls were pumped with beads and found that there were no beads present at that level. They had watched the installers pump the beads in and they were definitely pumped to that level.

A thermal image camera survey is the only viable way of proving this, bar drilling holes all over the place...

You don't need to drill holes all over the place. You've just made a good call on the beads settling. All that's needed is a 10mm masonry drill bit and a power drill. Drill out the joint where the vertical mortar joint meets the horizontal. You should be able to see the beads through the 100mm/4" deep hole with a torch. If you need a bigger ope to see, you can drill holes vertically above this and knock out any remaining joint with a chisel, taking care not to crack the brick. If this still doesn't work you can work your way along and remove ONE brick. You should be able to get a small digital camera in with a flash to photograph what's happening in the cavity. Alternatively you can do as Shane says and get a Thermal Imaging "map" of the external envelope of the house done. ONQ [broken link removed] All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken. Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.

Shane007 said:

... I am wondering with the fall in temperatures, is this becoming a more common problem. Does cavity wall insulation hamper the natural breathability of a dwelling, in general terms of course?

Click to expand...

I am seeing this being the case in my house. Never had a mould issue in kitchen until i had the walls pumped. Problem seems worse around windows.

This might be worth reading

Quote:

Many readers complain that, following cavity wall insulation, they have suddenly started to experience "increased condensation". They often to put this down to a decrease in the "breathability" of their walls (or to the blocking-up of airbricks by the CWI installers - a surprisingly common occurrence), and compensate by opening windows to dry their homes out. They do not realise that the source of the extra water running down their windows and dripping from their ceilings is rainwater penetrating via the cavity wall insulation, and so have not bothered to report it to anyone.

Hoagy said:

This might be worth reading

Quote:

Many readers complain that, following cavity wall insulation, they have suddenly started to experience "increased condensation". They often to put this down to a decrease in the "breathability" of their walls (or to the blocking-up of airbricks by the CWI installers - a surprisingly common occurrence), and compensate by opening windows to dry their homes out. They do not realise that the source of the extra water running down their windows and dripping from their ceilings is rainwater penetrating via the cavity wall insulation, and so have not bothered to report it to anyone.

Click to expand...

Very interesting article. I am finding this a big issue of late with many problems coming to light. This topic could do with a lot more input and debate...

Excessive humidity in the air will condense on cold surfaces. Before cavity wall insulation it would have condensed over a wide area of exterior walls and might not be noticeable due to this wide thin spread. After cavity wall insulation there will be less cold areas and as the same quantity of water will condense it will be very heavy and noticeable in these smaller areas. You can increase ventilation to prevent this or dry these smaller areas of condensation with an old towel regularly to prevent mould growth.

i tend to agree but with the exception of the towel solution- i would prefer solving the problem, which is about ventilation and consideration/understanding of thermal bridging (which should be solved not covered over) and the right wall/roof build-up where increased insulation is proposed

imo the ask-jeff link is out of date, the discussion is and the picture is about loose mineral wool used in a cavity, not the beads that are now being pumped

we often get ventilation and air-leakage confused, or to put it another way: we live in leaky homes but not necessarily well ventilated homes. the average client/ home-owner often doesn't appreciate this, or the fact that their parents generation (without the insulation remember) were great for opening up their windows and replacing the air in their homes regularly. traditionally we had a sporadic heating methodology, whereas now we want continuous heat at 21degs and in doing so, were concious of cost and don't want our heat escaping.

we generate water vapour, as does some of our heating systems, our cooking, drying etc. we also confuse the term 'breathability', referring to it while discussing ventilation, when it should be discussed when referring to the 'Water Vapour Diffusion rate' think gore-tex! think cob, earth, lime built homes or timber frame with the vapour checks in the right places..

we must consider the 'breathablity' of our building fabric's but, we must also consider ventilation more carefully. this is especially relevant with retro-fitting and it demands that our specifiers and builders make provision for better air-changes to reduce the RH in our homes