• Wednesday , 8 April 2020

Design Clinic: Replacing Windows

Design Clinic with MRIAI Ciarán Ferrie


Q. Hi..can you advise please. We have aluminium double glazed windows which are approx 25 yrs old. We want to do something to upgrade so we can keep more heat in. Should we

  1. A) replace the windows with uPVC and better glazing…or
  2. B) upgrade the glass only to double glaze with low u value glass.
  3. C) do nothing as we will not get any return on our money

Money is tight as we are pensioners. There is nothing wrong with our current windows other than that we get condensation on the glass and frames when it is cold outside which is a nuisance and it blackens the wall around the frame. Window people  tell us that improving the glazing is virtually useless with aluminium frames as we will loose the heat through the frame so we need to change the windows to uPVC and upgrade the glass. Glass people tell us upgrading the glazing is enough. We are totally confused  and see that each has a vested interest so any advise would be a great help.

Thank you

Anne Marie F.

Answer by Ciarán Ferrie, MRIAI

Dear Anne Marie,

Your existing window frames, given their age, are probably quite thin and will have much lower thermal insulation properties than even the most basic of modern windows. Replacing the glass on its own is not going to solve the problems you describe and I would recommend replacing the windows in their entirety.

The blackening of the walls around your windows is likely to be a form of mould which is caused by moisture build up on the walls through condensation. The condensation is itself evidence of poor thermal performance in the windows, and possibly in the surrounding wall, as well as poor ventilation of the room. Mould can be a serious health hazard if allowed to grow unchecked and any solution to your window problem should seek to eliminate this risk.

Replacing the windows will also give you an opportunity to have the window jambs inspected – it may be necessary to install some cold-bridge insulation and/or a damp proof course to the jambs before new windows are installed. This will reduce condensation build-up on the walls around the window and will lead to a warmer internal environment.

There are many different types of windows on offer in the market today, from uPVC to Timber to Aluminium and “Alu Clad” (timber frames clad externally in Aluminium) and all will provide you with a much improved thermal performance than your current windows.


Whichever material you select, one of the key issues to look out for is the “U-value” of the window. U-value is the measure of the rate at which heat passes through a building element – the lower the U-value, the better the performance.  When requesting U-value figures from window suppliers make sure that you are getting figures for the whole window unit and not just the glazing. Poorly performing frames will reduce the overall performance of the window even with high performance triple glazing.

Fitting the window frames with “trickle vents” will allow passive ventilation of the room even when the windows are closed. This will contribute to a reduction in the build-up of condensation in the room.

If all this is beginning to sound like a large investment there are a number of schemes which you may be able to avail of to ease the burden. The Home Renovation Incentive Scheme was recently extended to the end of 2016. This allows you to claim a tax credit for VAT paid on renovation works to your home up to a maximum credit of €4,050. You can find more details of the scheme on the Revenue Commissioners website at http://www.revenue.ie/en/tax/it/reliefs/hri/.

The Housing Aid for Older Persons Scheme provides grants for people over the age of 66, subject to means testing, to have necessary repairs or improvements carried out to their homes. The effective maximum grant under the scheme is €8,000 which may cover up to 95% of the cost of works. Details of the scheme can be obtained from the Housing Grants Section of your local authority.

Ciarán Ferrie is principal of Ciarán Ferrie Architects and a director and founding member of Fumbally Exchange http://www.cfarchitects.ie/


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