Aluprof UK > Articles
Published on 30 January 2019 13:07

Thermal Design Choices for Aluminium Fenestration Systems

(Page 1 of 5)
1
2
3
4
5
Key Learning outcomes
  • To understand the benefits of specifying thermally insulated aluminium.
  • To have a basic knowledge of aluminium thermal break development.
  • To be able to interpret basic thermal simulation graphics.
  • To be able to identify issues of cold bridging and how to avoid.
  • To be able to select a system design to suit the buildings’ requirements.
Forty years ago we were installing solid aluminium frames in most applications with single glazing, today, designs and systems have changed a lot.

There are now various ways to insulate aluminium to ensure thermal efficiency. This CPD looks back at the history of thermal breaking of aluminium and brings the process up date with the latest technology. For the specifier it is important to note what type of thermal break should be used in which system and to determine the suitability of the system to be chosen for any given project.

Whilst we are not trying to make window designers of specifiers, it is important to understand what constitutes a competent aluminium fenestration system. These five learning objectives should give you a better understanding of the efficiencies that can be made by specifying modern aluminium fenestration systems.

1.0 So why insulate?

Well apart from the obvious legislative reasons, we can make our buildings more comfortable with the right product design.

The Building Regulations, Approved Document L is all about the conservation of fuel and power, basically insulation requirements, there are four documents:

Approved Document L1A:
conservation of fuel and power in new dwellings, 2013 edition with 2016 amendments
Approved Document L1B:
conservation of fuel and power in existing dwellings, 2010 edition (incorporating 2010, 2011, 2013 and 2016 amendments)
Approved Document L2A:
conservation of fuel and power in new buildings other than dwellings, 2013 edition with 2016 amendments
Approved Document L2B:
conservation of fuel and power in existing buildings other than dwellings, 2010 edition (incorporating 2010, 2011, 2013 and 2016 amendments)

So where does the heat loss occur through a window system? There are three main areas, that of conduction, convection and radiation.

Convection - air circulation in a window profile cavity - about 35% of the energy flow.
Conduction - through solids - about 50% of the energy flow.
Radiation - from a warmer surface to a colder surface - about 15% of the energy flow.

There are many books written on the subject of condensation, but the control of condensation comes down to two basic criterion, that of good window insulation, which reduces heat loss and good ventilation, which reduces air moisture.

Used externally there is an issue of surface spread of flame if used over 18m in height where dwellings are concerned. All external finishes must be capable of achieving a rating of A2-s1, d0, a limited combustibility material or A1 a non-combustible material. Powder coating meets the requirement for the A2-s1, d0 rating. Window and door frames, including curtain walls are exempt, but infix panels and column casings for example are required to comply. The specifier should ensure that where dwellings are located within buildings over 18m in height that materials do meet a minimum rating of A2-s1,d0.
An example of the ‘fill and de-bridge’ design of thermal breaks which were introduced about 40 years ago.
An example of the ‘fill and de-bridge’ design of thermal breaks which were introduced about 40 years ago.
 
(Page 1 of 5)
1
2
3
4
5
 

About

Unit 5a
Altrincham Business Park
Stuart Road
Altrincham
Cheshire
WA14 5GJ
Kevin Mellor
Tel + (0) 161 9414005
kmellor@aluprof.co.uk
The information contained in the CPD article web pages is not intended and accordingly shall not be relied upon either as a substitute for professional advice or judgement or to provide legal or other advice with respect to any particular circumstance. RIBA Enterprises accepts no responsibility for loss occasioned to any person acting or refraining from action as a result of the information contained.
Download PDF version