ventilation in timber frame house

We live in a timber frame house and feel the house is not properly ventilated, despite having vents and leaving the windows opens. In fact the whole house gets stale air very quickly and smelly if the windows are not open. an anyone tell me what are the requirements for ventilation in timber frame houses? We have noticed that there are plactic looking studs in the walls (protruding from external walls) in our neighbours houses but we only have a few. Is this a requirement of timber frame constuction? Any advice appreciated

KOS

Hi KOS, I can't answer your query..but I'm sure others here can as a fair few building experts do visit this forum from time to time...what I would ask though...have you had this built by a reputable timber frame co such as Century or Cygnum.... if so, they should be in a good position to provide follow up advice/support...

ninsaga

Hi Kos

It looks like the inside of your house is lined with plastic/polythene just inside the plasterboard as a vapour barrier, (you know what happens if you put your head inside a plastic bag).
This should have been a more expensive breathable membrane.
But the best option in my opinion for people who are interested in timber frame housing is Softboard Technology.
You put Softboard impregnated with latex on the outside of your house and normal softboard on the inside with insulation in the middle between the studs.
This gives you a totally natural breathable wall with a high U-value that regulates the inside temperature and moisture levels perfectly and gives high levels of airtightness.

i was about to put up a vapour barrier under the plaster board in a new timber frame when one of the TF suppliers said if it was his house he wouldnt bother and that it was a homebond regulation. he said that he never met any one yet that could explain what their exact function is and if there was damp coming through on to the plaster board you could rectify the problem right away but with the vapour barrier it could be hidden for years.

It is always difficult to confirm the definitive cause of this problem over an email but in my opinion the problem is associated with two key points.

1). A lack of attention to detail and airtightness at the build phase

2). Inappropriate materials (i.e. a vapour barrier) on the warm side of the construction

A timber frame construction should be as diffusion open (breathable) as possible on the outside and as diffusion tight as necessary on the inside.

I assume that this building was constructed with a vapour barrier ineffectively sealed. As a result of this; excessive moisture was transported into the structure and at this stage has accumulated leading to ideal conditions for moisture induced problems and high levels of heat loss. The excessive amount of moisture leads to mould growth which may be the cause of “stale air”.

The solution is dependant on the extent of the problem. There is a diffusion open “breathable” membrane available called pro clima INTELLO.

This membrane is installed instead of a vapour barrier and increases the safety for the structure by a huge degree. It was developed by a company in Germany called pro clima and is available from Ecological Building Systems.

The only way to realise the extent of the problem is to investigate and that means removing a plasterboard I’m afraid….

What about measuring the humidity levels in the house?
What is the area of the vents in place and the volume of the rooms they are servicing? Someone may be able to guestimate air changes per hour based on this.

Thanks for all your suggestions and advice.
Could someone explain what is meant by a vapour barrier, as surely this stops the inside of the house "breathing" and stops fresh air getting in to the house? I know that timber frame houses need to have a breathable membrane and I don't know what was put into our house, as we bought it second hand.
As regards the vents, there is no vent at all in one bedroom, one is half blocked in about bedroom with a built in wardrobe and the there is no vent in the bathroom. The two ensuites have alectric extractors but one does not seeem to be much use at all. I presume that as a minimum there should be a vent in each room?

If there is damp building up in the house, would we see it? The house is built on what I would term "very wet" ground.

How do you test the humidity in the house - is this a job for an engineer?
We really feel at this stage that something is not right but are finding it difficult to put our finger on it. Would CO2 levels be high in the house if it was not veltilated properly?

Thanks to all

is the safety of the hosue compromised by the lack of appropriate breathable membrame, as I find sleeping is difficult due to lack of frash air in the house?
If the house does not have the corret breathable membrane, is it a correctable fault or are we stuck with it?

What is a wind blower test?

Is the house supposed to be airtight.....I am getting confused. I though being airtight was the problem?

A wind blower test can be referred to as a Blower door test. This is a device which measures the airflow through the building using a high powered fan. You can compare it to blowing up a ballon with no holes..this is airtight...but if it has leaks...more air is required to blow it up...and it is therefore "leaky". The ballon can be used as an analogy for the vapour barrier around a timber frame house.

A "leak" in the baloon can represent allot of heat loss and a path for moisture laden "warm" indoor air to travel into the structure of the building.

If the building is relatively "diffusion tight" on the outside and the "moisture loading" (i.e. the moisture getting in via leakages), is high then over extended periods this may lead to mould growth.

Airtightness is an important part of constructing a healthy building, but of course ventilation is also critical if the building is going to be so airtight. The healthiest timberframe constructions are those which are airtight on the inside but open to drying out in the event of unforseen levels of moisture getting into the structure...this is where it gets more complex and "breathabilty" becomes an issue. A vapour barrier on the inside taped and sealed is essential but idealy a product which acts as an airtight seal but is sufficiently open to dry out in the event of moisture entry is preferable.

I think a blower door test would quite quickly tell you how "airtight" your building is.

Just one other thing. In my original post I mentioned "studs protruding from the external walls in neighbours houses". These, we have since discovered, appear to be "weep vents". Does anyone know what is the requirement for these in the external masonry of a house, especially a timber frame house? Is there a problem if they are plastered over instead of open (presume if plastered over they are ineffective???)
I know from some research that mesh ones can be used but the ones in our house are plactic, about 2 inch long vertical with small holes. Would a lack of these mean air is not circulating in the house?

Thanks for all the advice and replies so far

It should be possible to get vents put into the frames of your windows, so at least adequate ventilation in all rooms without having to make holes in walls and the mess and possible structural issues this would entail.

There should be no uncontrolled (unwanted!) airflow through the fabric of your house. Weeping vents are - I'm only a builder amateur - completely useless for a pure timber frame building. Only if you own a brick cladded house where the outer brick/block wall and the outer joints(window sills,-frames,sewer pipes etc.) are of poor workmanship -because they give way to penetrating moisture- then you need weeping holes. To get rid of the water that might acumulate in the cavity.

Of course these weeping vents are useless when the holes are not open.
A cavity wall that is punctured with holes is a badly insulating wall. Think about a cladding that would make the wall watertight , then you could use the existing cavity (after filling it with insulation material) and the ex-brick/block wall as an extra heat insulation.

Waht do you mean that they are inneffective in a timber frame house - should they be there or not? Niighbours houses ahev them, in fact have more of them that we have. Surely they have a ventilation purpose to allow the external part (outside the timbe frame) to breathe. My concern is that this is not happening becaouse of the lack of them and therefore the house is "sweating" which would cause damp and the timber to rot, possibly? There is definitely a problem with stale air and lack of fresh air in the hosue generally.
Is there anything that can be done if the weep vents should be there and are not - can it be rectified now?
How can you find out if there is damage done by lack of them and is it a problem Homebond should rectify?

You could contact Homebond and ask them. If you're not happy with the house then why haven't you gathered more information before deciding for it? Sorry, I don't want to rant. There is a lot of literature available on the market covering the issue of "sick building syndrome"-from your description I take it that this is the issue with your place.
Every house is different. Cladded timberframe is not the same as pure timberframe where the outer wall could be of plastered timber for example. A watertight wall makes weeping holes useless-what water should they "weep"? Water vapour coming from the inside of the building through the wall and hitting a cold spot (for example the second wall/cladding/pipework) will condensate and cause build up of moisture. Therefore there are rules how to build a "breathable wall" . These rules have one fundamentally important thing in common: Water that goes in must be allowed to come out. As Niallcrosson has said.
To give you a somewhat more picturesque description: Think about a piece of cardboard. Put one drop of water on the surface and see it vanishing in the carboard within a minute. That would be "taking up" of moisture. Now wait and see for another minute. The water drop will reconstitute at the other side of the cardboard! Well, just in fantasy, but that is how a breathable wall works. This building technic is not understood by most builders here in Ireland and hardly any bloke on the site has ever heard of it. But when the weather is bad you see them wearing Goretex and Sympatex clothing. Not understanding how it works they make use of the technic.
And to build a breatheable wall is for the avarage bloke so complicated as weaving a piece of fabric. Without proper training -hopeless.
So I would say: Go the legal route. Check with a lawyer what the situation is, who should be contracted to write a watertight report to be used as evidence. And when you have fought the case you will have learned more about building with timberframe then the staff on site will ever do.
Good luck.

Not so much a musty smell but there is a stale air smell (like you would get in a car if you had 4 people in it for 4 hours and not stopped or opened the windows once) It is like when we breathe the air stays in the house and there is no new fresh air getting in.

Hi Kos, there are a few very good American books about timber frame by Larry Haun, published by Taunton Books. I've just got my local library to buy "Energy efficient Building" by Taunton Press - very good stuff about ventilation and insulation. It all had me pretty confused for a while but now I see the sense in it as follows:
(this refers to a timber frame house with timber cladding on the outside and no cavity) Behind the cladding on the outside you have a breathable membrane (housewrap) which stops rain and damp getting in but allows moist air and condensation to escape to the outside and allows the inside to dry out on dry and windy days. However, on the inside, you must ensure that internal house-generated condensation (cooking, bathing etc..) does not get into your walls as it could condense there and wet the timbers. So you fit an impermeable barrier on the inside surface of the wall, behind your plasterboard, to stop any moisture in the house getting into the walls. So, you say, how does the house breathe? Answer: a ventilation system. Does'nt have to be complicated - could be just opening windows, trickle vents built into windows, extractor fans over cookers and in bathrooms etc.. So, you let the house breathe but not into the walls - it breathes through windows, doors, vents fans etc... It appears that it's essential that the the waterproof impermeable barrier on the inside of your timber walls is very well fitted with no tears or breaks (well sealed at openings, window edges, sockets, pipes etc..) - the moist air will go straight for the gaps and holes if it is the easiest way to escape. Good luck in your endeavours.
Atmop
ps: Please, everyone, ask/annoy/badger your local library to throw out all those rubbish 1950s 'building' books (including horrible 1970s bungalow plans books) and buy the latest on design, building, heating tech etc...

That was good advice, Atmop! Thanks.

These vents are supposed to be every 700mm at the top of the external wall to allow the timber frame to breath but as regards the ventilation of the house i can't help you on that one.