Not all windows are the same...

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Buyers guide

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Not all windows are the same...

This guide has been compiled to help you make an informed decision when selecting and purchasing your new windows and doors.

Everybody will tell you that their product is the best. We feel the infor- mation contained in this guide can help you understand the differences between windows and help you choose what is right for you.

If you do not find the answers you need in this guide or if we can help you any further, contact us on LoCall: 1890 411 411,

info@gradyjoinery.com or visit www.gradyjoinery.com

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U-Value…

Essentially a U-Value is a measure of a windows ability to keep heat inside your home and cold out. The lower the U- Value the more heat you will keep in your home.

A low U-Value means less waste of the heat you pay for and less carbon emissions.

Solar Gain/Solar Factor…

Solar Gain is a measure of a windows ability to transmit free heat from the sun into your home.

A higher Solar Gain value is better, but this means nothing if you have a high U-Value, the free heat gained will go straight back out your window. A high Solar Gain can also lead to over heating in summer when you don’t want any heat.

A-Rated…

Windows can be rated against an energy efficiency scheme (WEP in Ireland, BFRC in the UK).

These schemes are a consumer aid but they are flawed, you can have a good A-Rated window and a bad A-Rated window. Manufactures can achieve A-Ratings in different ways…

 You can have a high U-Value, compensate with a really high Solar Gain and still achieve an A-Rated window.

 Glass is the most efficient part of a window, you can use lighter frame profiles to get more glass in and achieve an A- Rated window. This is not good for durability or longevity.

 Steel is a must for the structural integrity of a window, yet by taken it out or replacing it with PVC you can achieve a better energy rating.

If a Rating is not independently certified, it doesn’t mean anything!

What does U-Value, Solar Gain, A-Rated mean ?

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What should I look for in a window ?

Shoot bolt locking systems -better security

Stainless steel hinges and hardware -durability and longevity

Independently certified & tested -peace of mind

- energy performance - certified for BER assessment ( Building Energy Rating )

- security, durability, weather resistance

Welded joints -durability and longevity

100% Steel Reinforced frames -a must for durability and longevity

without steel a window has no structural integrity, also handles, hinges and locks are screwed only to PVC and will loosen over time.

Internally glazed -better security

Argon gas filled glazing units -better energy efficiency Warm Edge spacer bars -better energy efficiency Low-Emissivity soft coated glass -better energy efficiency

Heavy duty hinges for triple glazed -durability and longevity Insulated frames -better energy efficiency Low U-Value -better energy efficiency

Zero air leakage -better energy efficiency Double sealed glazing units -durability and longevity

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What should I avoid in a window ?

Not independently certified & tested -no peace of mind - energy performance - not certified for

BER assessment ( Building Energy Rating )

- security, durability, weather resistance

Mechanical joints -structurally weak No Reinforcement or -structurally weak PVC Reinforcement

Externally glazed -less secure Air filled glazing units -increased heat loss Aluminium spacer bars, -increased heat loss Foam spacer bars

Hard coated glass -increased heat loss No Insulation -increased heat loss High U-Value -increased heat loss

Co-Extruded profiles, -increased heat loss through draughts Glazed or Frame vents

Hot melt glazing units -structurally weak

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Are all glazing units the same ?

No - all glazing units are not the same, all double are not the same and all triple are not the same.

How good a glazing unit is will not only depend on what materials it is made with, but also how it is made.

Hermetically Sealed Insulating Glass Units

This is the technical term for a double or triple glazing unit. The two key terms here are hermetically sealed and insulating.

Hermetically Sealed

There are two types of seals Cold Fusion and Hot Melt, in our opinion a Cold Fusion seal is better because it offers two seals to the glazing unit and can only be manufactured using a ridged spacer bar which again is better. Hot Melt units are cheaper to manufacture, have only one seal and use a foam spacer bar.

If a unit is not sealed perfectly and built to last it will not perform efficiently and ultimately will fog up.

Insulating

Convection is the transfer of heat through the movement of gas, different types of gas are used to fill glazing units and prevent convection.

Argon and Krypton are the two main gases used, Krypton is a lot more expen- sive than Argon and only performs better in a narrower cavity. The chart below shows the cavity widths where the different gases perform best.

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The U-Value of a glazing unit will depend on many things…

 type of glass used...

...low-e soft coat, low-e hard coat, low iron, etc.

 type of spacer bar used...

...warm-edge spacer, aluminium spacer, solid or desiccant filled

 type of gas used to fill the internal cavities...

...argon, krypton or air

 width of the internal cavities...

...12, 16, 20, etc.

 number of internal cavities...

...1 double, 2 triple, etc.

 type of sealant used to seal the unit...

...polysulphide, polyurethane

As with windows, the lower the U-Value the better the glazing unit will perform.

Glazing units with a 0.6 U-Value for triple or 1.1 U-Value for double will give you the best overall window performance, but only when combined with a good quality insulated frame.

We recommend…

0.6 triple or 1.1 double glazed with...

 low-e soft coat glass

 argon filled

 warm-edge spacer

 cold fusion - double sealed

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What type of windows should I buy ?

uPVC Casement

U-Value - 0.8 ( with 0.6 U-Value Glazing )

∙ air leakage =0 ∙ cost €250( approx.900w x1400h )

∙ annual energy cost - €0.00∙maintenance cost - none

∙ life span - 30 years+

uPVC Sliding Sash

U-Value - 1.4( at best with 1.1 U-Value Glazing )

∙air leakage >0∙ cost €530( approx. for double glazed 900w x1400h )

∙annual energy cost-€147.00 ∙ maintenance cost - none

∙ life span - 20 years

Timber

∙air leakage >0∙ cost €410( approx.900w x1400h )

∙annual energy cost - €73.58 ∙ maintenance cost - high

∙ life span - 15-20 years

Alu-Timber Clad

∙air leakage >0∙cost €480( approx.900w x1400h )

∙annual energy cost - €98.00 ∙ maintenance cost - moderate

∙ life span - 20 years

Aluminium

∙air leakage >0∙cost €550( approx.900w x1400h )

∙annual energy cost - €98.00 ∙ maintenance cost - none

∙ life span - 30 years+

The following is a list of different type of windows and how they compare against each other when glazed with 0.6 U-Value triple glass units.

(PVC Sliding Sash - 1.1 U-Value double glass units, triple not available).

As you can see from below the frame type is very important and uPVC not only performs the best but it is also the most cost effective.

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What are the savings ?

Annual Energy Cost is based on the difference between installing 20m² of 0.8 U-Value PVC casement windows versus installing 20m² of the other options at current energy rates, does not include factors for air leakage or any provisions for carbon taxes.

Not buying the right windows will ultimately cost you money.

Inferior windows will need to be replaced sooner and less energy efficient windows will cost you money every day, below is a chart of annual saving based on today’s fuel prices that can be achieved by selecting the right windows.

We believe that the following specification is the way forward for energy efficiency, comfort and real savings for years to come.

Walls - 0.15 U-Value Windows - 0.8 U-Value

Ventilation - Heat recovery system (min 3 air changes per hour)

The above will give you negligible or zero heat bills.

Remember the lower the U-Value the more heat you will keep inside your home. An A-Rating is useless when a window has a high U-Value.

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