# Window Manufacturers



## house (16 Feb 2010)

Hi all,

When requesting a quote for windows and doors does Pilkingtion glass comes as standard or does each manufacture have their own particular brand of glass?

Is the uValue my main concern or should I insist on Pilkingtion (as its seems to be the market leader) ?

Thanks 
House


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## Bertie (3 Mar 2010)

not 100% sure but i reckon they all have their own brand. what ever you do stay clear of marvin windows imported from US. dont meet u-value requirements apparently, they list the imperial u-value but infact the metric u-value is well below standard! becomes a problem when getting BER cert.


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## RKQ (4 Mar 2010)

Imperial u-value? Can you substanciate this.
Marvin are a respected manufacturer, with a proven track record. ( I've no connection to Marvin)

Double glazed timber windows will have a certain u-value and a certain BER rating. IMO this will not make a huge difference to your actual BER result (unless you compare it to single glazed iron windows!)

Pvc and aluminium windows can suffer where the external temp. meets the internal *in* the frame, whereas solid timber is a good natural insulant.

Pilkington are a major glass manufacturer, supplying most window manufacturers. Most double glazed windows have the option of Argon gas - this is well worth specifying in your windows.

Do your home work, cut out the speel and try to compare like with like when comparing quotes.


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## Chocks away (4 Mar 2010)

RKQ said:


> ...........
> 
> Pvc and aluminium windows can suffer where the external temp. meets the internal *in* the frame, whereas solid timber is a good natural insulant. ..............


What is the reason for this reaction?


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## NHG (4 Mar 2010)

PVC is hollow in the centre with box hollow section steel in the centre whereas timber is solid the whole way through....


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## DBK100 (4 Mar 2010)

RKQ said:


> Imperial u-value? Can you substanciate this.
> Marvin are a respected manufacturer, with a proven track record. ( I've no connection to Marvin)
> 
> Double glazed timber windows will have a certain u-value and a certain BER rating. IMO this will not make a huge difference to your actual BER result (unless you compare it to single glazed iron windows!)
> ...



A few points to bear in mind:

Windows do not / can not have a BER rating. 
A Building Energy Rating is associated with a Building only.

The traditional method of measuring a window’s performance is through its U-value. This can often be confusing as there are 3 types of u-value that can be quoted:
1) The u-value measured through the centre of a glazing unit alone – ‘centre-pane’
2) The u-value of the window frame alone.
3) The overall u-value of the window including glazing unit and frame. – ‘overall’
Note: it is common for window manufacturers to promote the ‘centre-pane’ u-value of a window rather than the more realistic ‘overall’ u-value.

A 'WEP' refers to Window Energy Performance and is a method for assessing the total energy performance of a complete window. 
Window energy rating clearly identifies the best performing window as a whole system rather than simply considering the frame or glass.
WEP is an independent scheme operated by N.S.A.I. to allow comparison between different products.

http://www.nsai.ie/Our-Services/Cer...ion/WEP-(Wind-Energy-Performance)-Scheme.aspx

Some window companies here refer to a 'WER' as opposed to 'WEP'. I don't know whether WER has any status, is just an error, or is a manufacturer's rating scheme of some sort.

Solid timber is not a natural insulant. It is not an insulant.
Timber conducts heat at a slower rate than other materials such as metals or masonry, but it does not insulate.
With Building Regulations requiring higher levels of insulation all the time, more and more of the building envelope surface becomes highly insulated, with less and less Cold Bridges. As the rest of the envelope improves the heat conducting properties of elements such as timber become more noticeable and effectively become cold bridges. Everything is relative.
Insulation is now required across the top of Timber joists at ceiling level as well as between them in order to prevent timber joists conducting heat as cold bridges.

Most companies who manufacture aluminium framed windows now design and make them to be 'Thermally Broken'. The extruded aluminium frame is not continuous from inside to outside, but the sides are connected by a material such as polyurethane. That way there is less heat loss through the frame and no condensation on the frame.

You need to check yourself how an aluminium frame or full window performance from a particular manufacturer compares to a timber frame or alu-clad timber window.

Glazing unit specification is important. Around 2/3 of the energy lost from a  standard window is by radiation through the glazing.
Consider: 
- Width of cavity between panes of glass.
- Argon / krypton (or the more expensive xeon) -filled cavities improves the window performance by reducing conductive and convective heat transfer.
- Low-E (emissivity) Coated Glass for south / southwest facing windows*. *Low E glass coatings work by reflecting or absorbing IR light (heat energy). The thickness of the Low E coating and the position in the window dictate how the window will perform. By coating the face of the inner pane of glass with metal or metal oxide, your house will stay warmer in winter and cooler in summer by permitting shortwave radiation from the sun to enter but improving the glass performance to reflect long wave radiation from your heating system back into the dwelling.
- Glazing units are spaced and sealed by spacer bars around the perimeter of the unit. The traditional material for a spacer bar is aluminium. The heat lost from thermal bridging through the metal is becoming more of a consideration. Stainless steel spacer bars are an improvement, but better performance is to be had through the use of non-metallic materials such as steel reinforced polymer, glass fibre or structural foam with a polysulphide seal. This is often referred to as ‘Warm Edge’.

After radiation through materials, air leakage is probably the biggest contributor to heat loss from a window, particularly in badly installed windows. The kind of opening method also determines air leakage – traditional sash windows perform the worst whereas simple casements are generally better. Leakage is also common around the frames. A combination of pre-fabricated frames and ill prepared wall openings on site have led to a significant number of badly fitted windows with gaps left over.


DBK100
http://www.mesh.ie


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## RKQ (5 Mar 2010)

DBK100 said:


> Windows do not / can not have a BER rating.
> A Building Energy Rating is associated with a Building only.
> 
> 
> ...


 
I fully agree.
_Timber conducts heat at a slower rate_ than other materials and this is what I meant. Naturally Timber in itselfs cannot be used as an insulation material. I did not meant to infer this in my post. 

It is important to ensure the pvc or aluminium frame is Thermally Broken, not all frames are thermally broken.

There are huge differences in the price of windows and doors, so it is important to do your homework, so you know what you are buying.


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## Brigid (7 Mar 2010)

This is very interesting and has answered questions I didnt even know enough about to ask!  I wonder if someone could guide me - our plans have large south facing windows, with the high insulation standards these days I am sure that there is a danger of the rooms overheating.  Do standard windows moniter the heat coming through or is there something else that one should ensure is present in the windows to prevent over heating? In our plans we have a balcony which will over hang one part of the windows - this could help but I don't want to loose too much light.  thank  you.  Brigid.


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## onq (7 Mar 2010)

A note on Insulators:

I want to put timber as an insulator into context.

Timber was considered an insulator for many years, because it is a poor conductor of heat.

The terms "conductor" and "insulator" in general physics may also refer to materials which respectively can and cannot conduct electricity.

These define the extremes of conductivity.

Conductors are typically non-organic homogenous materials where electrons are free to move around to carry the electrical charge.

Many metals are electrical conductors.

Insulators are typically nonhomogenous materials - mixtures of substances, bodies of living organisms or organic compounds.

Timber is the body of a tree which is composed of many small cellular structures whose walls are made from carbon compounds.

Compounds elements are complex in composition where electrons are bound more tightly to atoms and so are poor at carrying current.

The mixtures are  disparate substances which are joined at the macro level so that current cannot easily be transported through the material.

Plastics, timber, concrete are all examples of electrical insulators.

Materials which are good at carrying current also are good at conducting heat [thermal conductors and insulators] and the opposite also holds true in many cases.

Air, trapped in cellular or fibrous materials to prevent large air movements is used as the basis for many so-called insulators.

Depending on how a building element is constructed this can be effective or less so.

Recent empirical studies have shown how insulation that is not tight to the inner leaf can allow thermal looping of air in the cavity to occur.

This takes heat from the space between the inner leaf and the insulation and significantly reduces its performance.

However everything is relative.

Everything except a vacuum conducts or convects heat to a greater or lesser degree.

But even a vacuum allows radiative heat, which is why you see spacecraft covered in reflective foil.

This ends your AAM University lecture Science 101. 

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.


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## onq (7 Mar 2010)

Brigid said:


> This is very interesting and has answered questions I didnt even know enough about to ask!  I wonder if someone could guide me - our plans have large south facing windows, with the high insulation standards these days I am sure that there is a danger of the rooms overheating.  Do standard windows moniter the heat coming through or is there something else that one should ensure is present in the windows to prevent over heating? In our plans we have a balcony which will over hang one part of the windows - this could help but I don't want to loose too much light.  thank  you.  Brigid.



I've read a lot about solar design which centres on the size of opes -vs- orientation and allowing materials within the building to heat up and act as heat stores.

I've read not a lot about the comfort of people living in houses without high tech window materials to modulate the incident suns rays.

I think you should google the passivhaus standard and ask your architect to devise methods of using solar gain while preventing overheating.

Hint 1: fixed overhangs cause shadows in even in winter that reduce the incident sunlight.

Hint 2: deciduous trees - without leaves - can significantly reduce the incident heat from winter sun on the house and don't provide a significant windbreak.

Hint 3: do not add a large south facing conservatory to a highly insulated house unless you are installing powered air conditioning - not MVHR, full aircon with cooling and humidity control.

Because in the summer you won't be able to stick the heat.

So be careful when using the old canards of overhangs, tree planting and conservatories to modulate the relationship of the house to the environment.

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.


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