Lofty whole home ventilation system - any good?

Very,very quiet. You should not hear it

Hi- I have a semidetached Victorian house which has a condensation problem. 2 adults and two children live there. They do not ventilate properly and do not have the heating on much due to the cost. The problem has reduced a little when I put in a tumble dryer to stop them drying clothes on the radiators. However, there is still a lot of condensation on windows and black mould on some walls and ceilings.

I've been looking into getting a Drimaster fitted. I was thinking of the 'Drimaster-Heat' as this would circulate some warm air if the temp in the loft drops below 10 degrees C. Can anyone recommend this product or give other advice?

Many thanks

I've decided to bite the bullet and purchased a Nuaire Drimaster for the loft and Nuaire NKF-1-H for the kitchen. It'll probably be a couple of weeks before they're installed but will post a message in Spring to update on how they perform when they're up and running.

I bought direct from Nuaire and their technical support were very helpful on helping me to decide on which product was for me.

The cost was:

£234.55 for the Nuaire Drimaster (including delivery)
£102.87 for the NKF1-H (inc delivery)

I`m looking at installing a loft PPS in my bungalow but does anyone have any experience or idea on how effective a loft Positive Pressure System is when fitted in a L shaped hallway of a bungalow? Does the air creep into and help reduce condensation in the rooms around the corner?
I have a loft conversion which restricts the fitting location.

I fitted a Nuaire drimaster in December 2010 and the results have been really good. The damp smell went within a few days and the condensation was reduced to a small amount at the bottom of the window, whereas previously the windows had been running with water, and there was mould on the curtains. Would definately recommend this product as a quick fix.

Hi, cant remember who it is that keeps saying to open windows but surely if the humidity outside is high (80+%) then there's not much point. Swapping 95% or even 100% humidity for 80% humidity wont bother the mould since it can grow anwhere the humidity is sufficient enough (cant remember the minimum humidity mould needs to grow but think it's approx 60%+).

Techgirl said:

Hi, cant remember who it is that keeps saying to open windows

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Me

Unless you live in some wet, swampy area, the cause of damp and condensation in an ordinary house in the UK will almost invariably be ventilation which is insufficient to cope with the moisture generated by the residents. Most often the causes are draping wet washing around the home, and using baths and showers without using an extractor.

If you live in a steamy jungle then a lofty won't help either since it is just another kind of ventilator.

Hi all,

Firstly there definitely seems to be a strong divide in the room between the 'open the windows' side and the 'it works side' and I cant work out which one Im on.

We have a 1930s house which I feel has adequate ventilation (but Ive not had a survey done by an expert). We dont heat the house alot as we cant afford the gas to be honest, the central heating comes on in the morning and evening but not over night. We have cavity wall insulation and plenty of loft insulation. We do occasionally have to dry clothes inside and the condensation is of course worse in those instances BUT even when we do not we still get condensation on our windows, the severity dictated by the coldness of the night as you'd expect. (John we do have a washing line but when its been raining for 1 week its not really any use!). We also have a bathroom extractor and the bathroom is no worse than any other room. In fact our bedroom is worst cos a - we are breathing in it and b - we generally have the door shut cos we'll be trampled by cats at inopportune times otherwise!

In the morning after a cold night I go round and mop off the condensation, open the windows and so on but its tedious and time consuming. It also makes little sense to heat a house and then open the windows to let the heat out after insulating it (!?!?)

Its not a massive problem but we do get spots of discolouration on the plaster/paper round some windows as its soaking up the water.

I understand the main causes of moisture in our house and expect it to be worse when there are more people staying or when we dry or cook alot.

What I want to know from people who have installed these systems is..

A - How much colder does it make the house, ie is it just paying to simulate opening a window
B - for those who have had success are your bills going up as you have to provide more heat to counter act the cold loft air (our loft space is freezing!)
C - has anyone carried out a few tests ie swithc it on for a week monitor temperature/gas usage, moisture buildup then switch it off.

There just doesnt seem to be any definitive answers and I guess thats partly cos every house is different but many now are heavily insulated and lacking a great ruddy chimney in the middle!

Cheers
Rolf

You will get condensation on and around your windows due to cold bridging, most double glazed windows are not that good, and in older properties you are prone to cold bridging the brickwork around the window.

If you have a 1930s house with cavity wall insulation, I would assume this is post blown into a 50mm cavity.

50mm of insulation will not make a huge difference (some), so your walls may still get cold enough for condensation, particularly in ceiling corners and openings (doors/windows).

A - How much colder does it make the house, ie is it just paying to simulate opening a window

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At the end of the day it's basically an extractor fan, turned round the other way, and on a low setting.

Think what it would be like to have a small fan in your window, and there you go, that's what it's like.

B - for those who have had success are your bills going up as you have to provide more heat to counter act the cold loft air (our loft space is freezing!)

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In a normal brick n block house, with typical cheap PVC windows installed, you are looking at about 10 air changes an hour, just from indoor/outdoor air pressure and temperature differential through gaps (gaps in windows, around windows, doors, letterboxes, pipes in walls).

In theory, if you go round sealing up gaps (for instance in poorly fitted windows), and have a positive pressure fan, it probably won't make much difference (other than the particular room it is in will be colder).

(And a house is not a submarine, even top notch windows and doors leak air)

Rather than air willy nilly coming in and out through gaps in the building fabric, you will with care be able to turn it into a kind of very slow wind tunnel, with dry air coming in, and wet air getting out, with probably at the same rate as you get through natural air changes anyway.

Thanks for that,

I am assuming that bridging is the cold in the outside brick layer being absorbed by the double glazing surround which makes it even colder and so more prone to condensation..is this correct..?

So in my case where I only have a small problem better quality windows which would create less condensation..?

To me it just doesnt 'feel' like a low power fan blowing some air into the upstairs hallway will make a lot of difference!

Rolf

I am assuming that bridging is the cold in the outside brick layer being absorbed by the double glazing surround which makes it even colder and so more prone to condensation..is this correct..?

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In most old houses with double glazing you get cold bridging around the brick surround to the window (the bricks surrounding the window, not the window frame itself), in most cases this is just due to poor installation, particularly in older houses. This is because you have the inner and outer block leaf, and the window is installed over the cavity breaching the (if any) insulation (either the window or non insulated plasterboard breaches over that cavity).

As to the window itself, I'm referring to the fact most double glazed windows are just cheap hollow PVC frames, and that they use metal glazing strips rather than more modern or expensive materials (this is the bit in the glazing unit that separates the two pieces of glass), the metal strips conduct rather than insulate, causing condensation around the edge of the window.

To me it just doesnt 'feel' like a low power fan blowing some air into the upstairs hallway will make a lot of difference!

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It will work, it's just a matter of how many air changes will be required to make it work.

Firstly with positive air flow through the fan, you will be pushing air through gaps around windows (blow air over surface = you dry the surface, just the same as if you breath on a mirror = condensation, but if you then blow air onto the mirror with a fan = condensation dries). Secondly of course you will just be lowering the amount of moisture in the air.

However if you have cold bridging, nothing will stop condensation forming on cold surfaces (other than 0% humidity), in most cases it will reduce it to a level where it is no longer an issue, e.g. a bit of fog around the glass and possibly the brick/plaster adjacent to the frame of the window.

If you have an older house, and you think of having this installed, I would recommend having a very good look at places air can penetrate, you want the air only to escape through window/door frames and vents, and because it has to be a positive pressure, to many holes = excessive air changes.

In a 1930s house, that could be a bit of a task. Light fittings in ceilings, sometimes sockets, floorboards if it's a suspended floor, pipes (particularly pipes in airing cupboards leading into the loft). If you have air bricks, leave them, but you might restrict them.

Think of your house like a wind tunnel, (whereas at the moment it's more like a sieve, with air movement going any which way) . When you turn it into a wind tunnel, you want to create enough air changes to dry the air, but not so many you can't keep it heated, balance it right and you could actually make it more and not less energy efficient (marginally)

We live in an 18 yr old bungalow (just moved in), we have a mould, damp problem above our window in our main bedroom that we sleep in and the windows run with water now winter has set in. We have a radiator in the room but cannot use it due to it being right behind my dressing table and I have nowhere else to put the dressing table so leave the radiator off but do put on the halogen heater and slim panel heater we have, on every night for about 6 hrs. Still we have black mould spores since we stripped and decorated the room 3 wks after moving in. No-one else in these bungalows (we are in a housing association complex) seems to have the same problem but they do use the CH in all rooms I believe. Also we are terraced so the bungalow is always warm although the bedroom is slightly colder if no heating applied plus obviously during the night the temp drops and the windows are running with water in the morning. The room is never cold enough to warrant any heating really but we are using the heating to try to solve the damp problem but nothing seems to work. Our bathroom is right next to the bedroom with the damp but we have just had a more powerful extractor fan fitted as the previous one packed up. However the damp is still there. We do have fitted wardrobes in this bedroom with top boxes and the damp seems worse above the topbox nearest the window.

What can we do to rememby the situation ?

Forgot to add, we have trickle vents in our double glazing in the bedroom also so cannot understand how a modern bungalow which is well insulated and warm can develop such a bad damp problem !

does anybody drape wet washing around the house and hang it on radiators?

JohnD said:

does anybody drape wet washing around the house and hang it on radiators?

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We are guilty of washing and drying it indoors in winter but we tend to put it in the kitchen right next to the radiator and keep the door closed. Tumble dryers are too expensive to run on a pension! How else can a pensioner dry their washing if the weather is too bad? Any suggestions?