Choosing the correct glazed facade heating system

There are numerous factors to consider when it comes to choosing an appropriate heating solution for glass façade buildings.

Andy Williams, Technical Consultant at Jaga, discusses the increasing demand for heating solutions which combat the practical issues regarding glazed façades, and how the correct solution can be determined.

[edit] Introduction

Contemporary building design shows that we have an increasing appreciation for natural light. That appreciation has manifested itself in the form of floor-to-ceiling glass windows, which have become an architectural feature in many new builds to create a sense of openness and space.

Take the capital for example, skyscrapers such as 20 Fenchurch Street, the Leadenhall Building, the Gherkin and the Shard have all been designed and built using glazed façades.

Glass is often chosen as it is a superb way of utilising natural light, reducing energy consumption, harnessing the solar comfort of the sun and insulating or interiors from noise pollution. Clean glass lines are also aesthetically pleasing, a crucial consideration for Architectural Technologists.

However, glass is notoriously poor at heat retention, and consequently buildings that are made up of glazed façades can experience high levels of heat loss — making warming the building a challenge. Additionally, glazed façades are extremely vulnerable to condensation build up.

The principle cause of condensation on the inside of glazed façades is high internal humidity levels, coupled with low outside temperatures — common in tall, multi-level, commercial builds. In order to maintain the aesthetic desired and prevent condensation and heat loss, the heating and ventilation in the areas where glazed façades are used needs to be thoroughly considered.

[edit] Be clear on the purpose of façade heating and cooling

When selecting a façade heating system, an important design aspect that must be considered is the purpose of the façade heater. The heating solution can be designed to provide effective space heating, mitigate heat loss, eliminate condensation, cooling and ventilation - or even be used for a combination of all of them. The intention of use will affect the preferred solution and will need to be considered early on in the design stage.

[edit] Trench heating: the ‘hidden’ solution

It is generally considered that trench heating is an ideal façade heating system due to its versatility. Whether it is the range of depths, widths and lengths, the option of grilles, there are numerous trench solutions available. A further advantage of trench heating is that it is a ‘hidden’ solution — it doesn’t take up wall space and can therefore be easily installed in front of floor-to-ceiling glazing, without impacting the aesthetic design.

Interestingly, it is also now possible for trench heating to not only heat, but to have the additional function of ventilating — and sometimes even cooling. Often in office and commercial environments, Indoor Air Quality (IAQ) is of particular interest, as correct ventilation can positively impact occupant health, comfort and productivity. Trench radiators can now be used to introduce fresh air by a direct connection to the outside, rather than using a separate ventilation system.

It is also important to consider that when cooling is to be included in the façade solution, additional power may be required to push the cool air up and throughout the room. This can be provided using a Dynamic Boost Effect (DBE) fan unit, which can be attached to the radiator in order to maintain rapid and accurate room comfort conditions, or a quick boost of heat if required.

However, as versatile as a trench radiator can be there are still times where trench heating is not viable for certain applications. These include when floor voids are either too shallow for trench heating or are completely solid, or where construction costs for creating trench channels are prohibitive.

[edit] Perimeter heating: the discrete alternative

In these instances, low-level, free-standing perimeter heating can be an effective alternative. Floor-mounted heating provides all of the benefits of trench heating — circulating and heating cool air from windows, minimal dimensions — but can be useful when technical issues will not allow trench heating to be installed.

Free-standing radiators can also be easily installed at the very end of a project, and can even meet Low Surface Temperature (LST) requirements. However, whilst perimeter heating is less visually obtrusive than other forms of heating, this system still takes up valuable floor space. For lettable spaces this is incredibly important, as the more space required for heating and ventilation, the less available space to let.

Certain types of trench and perimeter heating also contain an ultra-fast Low-H2O casing element which is either hidden under the grille or within the radiator. This element means that only a tenth of the water is required to heat the system when compared to standard, steel-panel radiators, which means that energy bills for the building can be reduced by up to 16%. Even though substantial energy savings can be made, the system will still remain incredibly responsive to temperature change.

[edit] As clear as glass

One thing is crystal clear. The number of buildings comprised of glazed façades are only going to increase over time. So, it is crucial that when design decisions are made on how the spaces that they enclose should be heated, aforementioned factors such as heat output, available space and aesthetics should all be taken into consideration.

This article was originally published in AT Journal Spring Edition 2017.

--CIAT

[edit] Related articles on Designing Buildings Wiki

• Articles by CIAT on Designing Buildings Wiki.
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• Double glazing v triple glazing.
• Emissivity.
• Glazing.
• Health and wellbeing impacts of natural and artificial lighting.
• How to maximise natural light.
• Lighting designer.
• Low-E glass.
• Preventing overheating.
• Secondary glazing.