Windows ConstructionChanging your windows for a better insulated home

Why change your windows?

The Principle

Our energy consumption has not stopped believing its last years bringing us an undeniable comfort of life.

Today, new technologies allow us to improve the energy performance of our home and thus save energy for our heating needs.

The walls of the house are the only barriers

between the inside of the house and the outside air.

The larger the surface area of these walls, the greater the heat loss.


Windows are sources of light and heat and therefore contribute to the heating of the house.

However, old windows let heat in and out as well.

Changing your old windows to newer double or triple glazed windows will improve your home’s thermal performance, acoustic comfort, closing security and air and water tightness.

The advantages of new joinery are therefore multiple and bring immediate comfort to the home.

The improvement in terms of insulation of the glazed walls acts directly on the heating needs of a house.

By installing double or triple glazed windows, you will save energy.

The simplicity of the work and the aesthetic improvement make it essential in the context of a renovation.Windows Construction

Better insulation by changing your windows: how does it work?

How does it work?

The walls of the house are the only barriers between the inside of the house and the outside air.

The larger the surface area of these walls, the greater the heat loss. Just like the walls, floor and roof, it is important to install double or triple-glazed windows with reinforced insulating properties.

Up to 30% heat loss is avoided.

Changing your windows in your home with double or triple glazing can save up to 10% of energy costs for heating.

The thermal performance of windows depends directly on the nature of the joinery (PVC, METAL, WOOD),

the performance of the glazing and the quality of installation.

The quality of the window is important for the airtightness that eliminates drafts. Caution, it is important to ensure that the house is well ventilated.

The quality of the glazing reduces the cold wall effect and reduces heat loss and humidity.

Double or triple glazing consists of two or three panes of glass that trap an air space.

There is also double glazing with reinforced insulation: one side of the glass on the air space side is covered with a thin invisible layer (usually silver-based) that acts like a wall, preventing the warm interior air of the house from escaping.

The insulation performance of double glazing with reinforced insulation is 2 to 3 times better than conventional double glazing and 4 to 5 times better than single glazing.

Be careful, the solar protections (shutters, blinds) are very important.

On summer days by keeping them closed, they provide comfort by preserving the coolness inside the house. On winter nights, they limit heat loss.

They also increase the security of closure against the risk of intrusion.Windows Construction

How do you change your windows? The implementation

Mise and oeuvre

Even if some techniques allow to change only the pane of the existing windows with the help of profiles allowing to fix them in the existing rebate, these solutions having a questionable efficiency in energy saving, we will not develop it here.


The implementation is the fastest and cheapest in the context of a window renovation.

The existing frame must not show any traces of moisture, oxidation, mould or significant deformation. If its general condition is suitable, it will be preserved and used as a support for the new window, which will cover it while maintaining good ventilation.

This operation does not involve any major masonry work or degradation of the walls, but it may slightly reduce the glass surface.


If the existing frame is not in good general condition, it will be imperative to replace the entire window. The same applies to the building’s architectural constraints.

This technique requires more extensive masonry work and therefore generates additional costs, but its thermal insulation and soundproofing are superior.

Changing your windows: What technical features to look at

Technical characteristics


As its name suggests, it is the window’s heat conductivity capacity in Watts per m² and per degree Celsius.  It depends on the quality of the glazing but also on the joinery.

The lower it is, the higher the performance of the glazing.

For good thermal insulation, it is recommended to have a Uw value lower than :

Windows or French windows in :

PVC: Uw 1.4 W/m² °K

wood : Uw 1,6 W/m² °K

metallic: Uw 1,8 W/m² °K


As its name indicates it is the capacity of heat conductivity through the glass.  The lower the conductivity, the higher the performance of the glazing.

For good thermal insulation, it is advisable to have a Ug value lower than :

– Reinforced insulation glazing (low emissivity glazing): Ug 1.5 W/m² °K

– Double windows (second window on the bay) with reinforced double glazing: Ug 2 W/m² °K.


In addition to the thermal qualities of the window, the transmission of outside noise to the house can be significantly limited depending on the acoustic index. It is advisable to have a sound attenuation index greater than 28dB(A).

PLUS OPTIMUM ENERGY PERFORMANCE: some manufacturers offer low-emissivity glazing with insulation reinforced with treated glass and/or gas strip (argon or krypton). These glazings are even more efficient than conventional glass.

What is the insulation cost of changing the windows in your home?

What is the cost?

Since the investment cost for changing windows varies according to the choice of joinery, the thickness of the glazing, and the thermal performance coefficients, it is very difficult to give an estimate of the price of an installation.


In addition to acoustic (reduction of outside noise) and thermal (no air leakage) comfort, the installation of double or triple glazed windows can reduce your home’s heating needs by 10%.

Tax credit for changing your windows A REDUCED INVESTMENT THANKS TO THE TAX CREDIT.

The French state wishes to help control and reduce energy consumption.

10% tax credit for equipment installed by a professional

What amount of expenses does the tax credit apply to?

The tax credit covers materials, excluding labour, meeting the characteristics.

What is the amount of expenses eligible for the tax credit?

For the same taxpayer and the same dwelling, the amount of expenses eligible for the tax credit may not exceed, for a period of five consecutive years between January 1, 2010 and December 31, 2015, the sum of € 8,000 for a single person, widow or divorced and € 16,000 for a couple subject to joint taxation. This sum is increased by €400 per dependant within the meaning of Articles 196 to 196B.

To find out your rights to the tax credit, you are advised to refer to the provisions of article 200 quater of the General Tax Code.

For the application of this measure, it is strongly recommended to refer to :

The website (page on the tax credit)

Article 200 quater of the General Tax Code, Article 90 of the 2005 Finance Act, Article 83 of the 2006 Finance Act, Article 109 of the 2009 Finance Act and Article 80 of the 2010 Finance Act.

The tax instructions 5B-26-05, 5B-17-06 and 5B-17-07

The decrees of February 9, 2005, December 12, 2005 and November 13, 2007 issued for the application of articles 200 quater and 200 quater A of the general tax code relating to capital expenditure on the main dwelling and amending annex IV to this code

Sections 81 to 83 of the 2012 Finance Act

Financial aid for floor insulation from the REGIONAL, DEPARTMENTAL, and ANAH.

Some regions, town halls or the ANAH also subsidize the installation of photovoltaic panels by granting financial aid. Find out more directly from these administrations or from your ESPACE INFO ENERGIE.

Reduced VAT for floor insulation A VAT REDUCED TO 7% FOR LIVINGS OVER TWO YEARS.


You reduce your energy consumption for heating your home.

This can represent several hundred euros per year.

Changing your windows: environmental impact

Environmental impact


By installing double or triple glazing, you limit the heat loss from your home.

Your heating needs will be reduced as a result.

A good insulation of the glass walls is a guarantee of energy control.

The energy saved in this way means as much energy to be produced and as many greenhouse gases avoided.

The environmental impact is then immediate and lasting for many years.


Renewable materials with very low environmental impact, a way to become a little more Eco-Citizen.