Windows and MHRV

Rock12

Hello, I am trying to decide on a window type and supplier for my new build. I am thinking of a timber window, triple glazed argon filled with a make up of 4mm(glass) 10mm(argon) 4mm(glass) 10mm (argon). These have a Window frame and pane U of 0.9.

My questions are;
1) Are UPC windows and seals up to the negative pressure of the air tightness and MHRV?

2) Are the timber windows a better window and therefore worth the extra money? Or is it just the look We pay for.

3) Is the make up of the window frame given wide enough or is it a triple glazed unit fitted into a double glazed window frame?

Thanks for any answers ideas or opinions given because I have done too many u turns on this topic and need a fresh view point.

fatty pang

At best that glazing unit will provide a u-value of 0.8 so a whole window u-value of 0.9 is rather optimistic, if thats what you are alluding to.

1. Different windows have different profiles and different seals, and as a result perform differently. Not exactly surprising is it. The standard test for air permeability, EN 1026, requires testing at positive and negative pressure differences. Ask your intended supplier what classification the window acheived for air permeability. The minimum standard you should consider would be Class 2 but if you are aiming for a reasonable lvel of airtightness you should only consider Class 4.
2. There are good and not so good examples of both around. if the purchase price is your primary criteria as is so often the case then you might wish to acquaint yourself with Ruskins common law of business balance. I would contend that overall the best windows are aluminium clad timber... but there are some pretty poor examples of this well entrenched in the Irish market.
3. As you haven't provided any information about the profile size its not possible to give a definite answer. That being said, a 32mm argon filled IGU is some way off the optimum width (44-48mm) for an argon filled triple-glazed unit. It certainly has more then a whiff of a triple-glazed unit being shoe-horned into a system designed for a double-glazed IGU. Last week I was asked by a service engineer acquaintance to look at a similar situation. We both knew how easy it would be to effect a forced entry through the window despite the sales pitch being centred on how internally beaded windows are ultra secure. The less said about it the better on this forum - I don't want to upset anybody. As long as the window is 'A-rated' who cares?
4. The answer to the question you didn't ask is the most important - check the certification for the window....and good luck because I think you'll need it!

BryanF

1:yes depends on the window
2: ye timber wins look better, if treated properly will last as long, aren't as carcinogenic, their recyclable/ lower in embodied energy, but for good thermally broken units will cost more.
3: depends on the unit, you generally pay a Preminum for quality units designed to best modern standards

We both knew how easy it would be to effect a forced entry through the window despite the sales pitch being centred on how internally beaded windows are ultra secure. The less said about it the better on this forum - I don't want to upset anybody. As long as the window is 'A-rated' who cares?

a good arch will look past 'A rated'. Why not elaborate about your forum conspiracy?

Rock12

Thanks for the replies, I am weary of the large upvc suppliers because I have read a lot of negative reports and with such a substancial investment I don't want to regret my decision for going with the upvc if the timber is a better window.

The dimensions above are for a particular window manufacturer in tha mid lands who says his glass has a U of 0.7 and the glass and frame give 0.9, I have seen their windows and they are a well made unit but I feel the 10mm argon gap may be insufficient. The Frames are tested to 900 pascals and the water and wind loading certs.

I suppose my question is if the Certs are to the same values, is it worth the extra money for timber from a quality point of view?

Thanks again.

fatty pang

BryanF wrote: »

1:yes depends on the window
2: ye timber wins look better, if treated properly will last as long, aren't as carcinogenic, their recyclable/ lower in embodied energy, but for good thermally broken units will cost more.
3: depends on the unit, you generally pay a Preminum for quality units designed to best modern standards
a good arch will look past 'A rated'.

Last as long ? Empirical evidence suggests timber windows last a lot longer. I was walking past College Green today and the windows in Trinity have been there well before plastic was invented never mind made into windows. A lump of plastic should last for ever and a day but windows are made from relatively thin extruded profiles that are joined by various methods and then subjected to some rigerous thermal and physical dynamics. The BBA assert UPVC is good for a 35 year service life but assess timber windows with only 25 years (they are looking at timber again so that figure will change). The good ones will last 35 years and more but some of the rubbish will have to be replaced in half that time. On the subject of carcinogens I would happily put a lump of plastic in my mouth but I'd pass on using VOC impregnated timber for a toothpick. The BRE Green Guide gives UPVC an 'A' rating for windows which is on a par or better then timber - not that I'd agree with them but thats for another day. PVC is also recyclable - that helped to get its Green Guide rating - but most of the recyclate is still factory waste rather then post-consumer waste.

BryanF wrote: »

Why not elaborate about your forum conspiracy?

No paranoia here pal. Mention names of windows and its edited out. I don't see that happening with any other product thats discussed in the forum. The OP is a good example of how little consumers know about windows and as a result are at the mercy of suppliers. If he was allowed to mention the name of the window he is looking at it would be much easier to provide an authorative opinion on it. A "good arch" may indeed look past an 'A rating' but its still common enough to see a spec for windows consisting of nothing more then 'PHI certified'. You'd like to think that anybody designing such a building would know a little bit more about windows...

fatty pang

Rock12 wrote: »

Thanks for the replies, I am weary of the large upvc suppliers because I have read a lot of negative reports and with such a substancial investment I don't want to regret my decision for going with the upvc if the timber is a better window.

The dimensions above are for a particular window manufacturer in tha mid lands who says his glass has a U of 0.7 and the glass and frame give 0.9, I have seen their windows and they are a well made unit but I feel the 10mm argon gap may be insufficient. The Frames are tested to 900 pascals and the water and wind loading certs.

I suppose my question is if the Certs are to the same values, is it worth the extra money for timber from a quality point of view?

Thanks again.

That is a low u-value for the glazing unit if it is as you describe. Who issued the 'certificate' stating 0.7?
A 10mm cavity is not optimal by any means but in itself there is nothing wrong with it.
As noted previously there are good and not so good timber windows available. How do you know if its good or not ?
A few things to consider;-
Is the window covered by a certification scheme?
What sort of window is supplied with the window, the glass, the ironmongery ?
Is it drained and ventilated design?
Dry-glazed or wet-glazed?
What quality of timber is used?
What method of preservative treatment (if any) is used?
Timber or aluminium horizontal glazing beads?
Outward or inward opening. Flush sash or stormproof?
Whats cyclic testing has been carried out on what size/weight window?
Is the glazing unit En 1279 compliant?
Enhanced security certified?
Does the manufacturer make this particular window or does he buy it in?
If he buys it in where from and who provides the warranty?

As I said previously - good luck !

muffler

fatty pang wrote: »

No paranoia here pal. Mention names of windows and its edited out. I don't see that happening with any other product thats discussed in the forum.

You have read the forum charter? No? Perhaps you should.

fatty pang wrote: »

If he was allowed to mention the name of the window he is looking at it would be much easier to provide an authorative opinion on it.

The OP did not name a window supplier or a type of window as it was irrelevant to the questions he asked. Please dont drag this thread off topic by commenting on the moderation here or what is contained in our forum charter.

Certified

Just my two cents worth. I would choose timber windows any day. In an ideal world I could wish that the plastic ones were never invented. However there are Upvc windows that are cheap and affordable, this automatically makes them a very attractive option.
There are always examples of good and bad for every thing but a good timber window will at least match but should easily outperform a good plastic rival on the longevity stakes.
Timber windows with a little attention can be made to look like new at anytime, my own, I estimate are about 40 years old and today still look beautiful. The Upvc ones after 15-20 years will look very tired and faded and just look depressing.
Also, it is not true that Upvc windows are maintenance free, if they are not maintained they will fail.

Rock12

I agree with you certified, the timber is far and above the better window aesthetically and the timber itself will hold up if treated for many years but would the seals and the argon fill remain and keep the unit efficient for that length?

My other problem is finding a timber window that has the width of the upvc units to make them equally efficient? It seems I can only get a good double glazed unit in timber.

Certified

Rock12 wrote: »

would the seals and the argon fill remain and keep the unit efficient for that length?

It is very likely that the weather seals on any window will need to be replaced years down the road, especially over 40 years. It is possible to get timber window seals that are backed by a 'lifetime time guarantee'. You would need to get something in writing from your manufacturer/supplier on that as some have zero cover for the weather seals.

The glazing should be sold with a guarantee to not fail for a number of years, the length depends on each company and this should be clarified before purchase. It should be noted that the glazing units used in both upvc and timber windows can actually be the very same whether it be double or triple glazing.
Design details of the window frames will have an impact on the longevity of the glazing seal keeping the argon gas in. If water/moisture is allowed to come into contact with them on a regular basis they will certainly fail sooner. A good window, whether upvc or timber would eliminate this problem.

Certified

Rock12 wrote: »

My other problem is finding a timber window that has the width of the upvc units to make them equally efficient? It seems I can only get a good double glazed unit in timber.

It is possible to get triple glazed timber units. I agree that they may be harder to find as the cheaper upvc window almost eliminated the timber variety from this country, so there are fewer manufactures around to choose from.

Rock12

I think maybe a well supervised fitting of the larger frame in upvc maybe the best option, I am meeting a glazing specialist next week for a chat on the units so I will have a better and more informed opinion then

On the windows and MHRV, does anyone have MHRV and if so would they recommend having all windows with opening or only half or is there a need for openings on the glazing at all except for the fire escapes in each bedroom?

Certified

Having no windows that open or having all of them openable will have nothing to do with a MVHR system. The seals used also have no impact on the system.
Your windows need only comply with building regulations and planning permission conditions

Rock12

Sorry I should have phrased that question differently. I meant in the practical use of a house with MHRV, do people find the need, say in summer time , to open windows to let cooler air in or at any other time are opening windows useful or will the heat recovery negate the use for windows with opening.
I ask because I am doing up a list for pricing windows and I would like to hear people's views on how many I should have as fixed pane and how many to have with openings. Thanks for any replies.

BryanF

Rock12 wrote: »

Sorry I should have phrased that question differently. I meant in the practical use of a house with MHRV, do people find the need, say in summer time , to open windows to let cooler air in or at any other time are opening windows useful or will the heat recovery negate the use for windows with opening.
I ask because I am doing up a list for pricing windows and I would like to hear people's views on how many I should have as fixed pane and how many to have with openings. Thanks for any replies.

Certified is correct here. Your arch should be advising on opening sashs as per Bregs. This purge ventilation requirement will be adequate for summer 'by-pass' of Mvhr