The correct installation of LED downlights balances safety, energy efficiency, lamp life, fire ratings and soundproofing. John Konstantakopolous explains.

In part one of this two-part series on downlight safety, I explained the basics of the building envelope.

The envelope is an extremely important feature of a building and is not well understood in Australia. The three basic elements are the weather barrier, the air barrier and the thermal barrier.

The completeness of the envelope is also important for enabling sound proofing, fire ratings and energy efficiency.

So, the more airtight a building is the less draughty it will be, thereby allowing insulation to work more effectively. For instance, conditioned air will be prevented from escaping, and air won’t bypass insulation.

In part two, I will address control gear ventilation, downlight barriers and the future of the industry.

Below ceiling access

Some barrier types can be installed from below the ceiling.

In some homes access into the ceiling or above the recessed light fitting may not be possible, yet installation of an airtight and insulation-improved product may be necessary.

Installing downlight covers from below also substantially reduces the chance of personal injury or ceiling damage. Installing a cover from below is a great option for reducing the amount of work in the roof.

However there are advantages to installing from above when possible.

You can resolve any uneven surfaces and fill insulation gaps around the cover to improve airtightness and insulation consistency of the building envelope, thereby removing the Swiss cheese effect that this sort of lighting introduces.

Control-gear ventilation

Control gear (as shown in Figure 1) always seems to be forgotten.

It should be understood that LEDs – like 12V halogen globes – have an extra low voltage (48V or less) input, and incandescent globes are primarily low voltage (240V) input.

A home owner can legally change a 12V globe and make an LED-to-driver connection. However an electrician must be called to make any 240V connection.

Having separate control gear means that it can be fitted external to the LED globe, thereby reducing heat dissipation in an enclosure.

It’s important that the enclosure is capable of keeping control gear from being submerged in insulation.

It’s also important to allow LEDs and control gear to operate in as cool an environment as possible. (They cannot just be covered in insulation and the fitting siliconed to the plasterboard.)

Summer heat

The ceiling space or loft area in a roof can get to temperatures of 50˚ to 70˚C.

LEDs that are designed to be enclosed in a cover and ventilate in conjunction with the cooler living-area air can benefit from an airtight barrier.

Some believe that fixed-head downlights are better because they have smaller holes, therefore have less air loss.

When a downlight cover is introduced and the fitting no longer forms the interface to the building envelope, an LED luminaire can benefit from being exposed to the cooler air of the living space.

The barrier and insulation act as a shield, protecting the fitting and the living area from extreme roof temperatures.

A VIPAC report commissioned by Efficiency Matrix shows this clearly.

When a higher loft or attic temperatures occur, a downlight barrier can provide thermal protection. It is predicted that the temperature inside the barrier would be 48C while the loft above was 71C. The light was turned off.

The future

LED lighting is already mainstream in the small recessed-lighting market.

The need to make the building envelope and thermal envelope as consistent as possible assisted in the development of the barrier Standard.

Further changes involve the use of insulation coverable downlight fittings that can be covered without a barrier (see Figure 2).

Requirements similar to those in New Zealand are under consideration. If accepted, these would become a requirement for recessed luminaires in AS/NZS 60598.2.2, called IC rating luminaires.

The different standardised solutions that can be implemented to achieve a similar result have significant differences. The following are based on the ratings used in New Zealand, although the principle of extending the building envelope remains the same.

AS/NZS 5110 barriers

A good quality airtight barrier (Figure 3):

• Insulates the luminaire from extreme temperatures in the roof.
• Includes an R-value in the barrier.
• Keeps insulation away from an LED Luminaire, reducing operation temperatures, improving lamp life and performance.
• Can provide a tested and reproducible sound proofing and fire rating.
• Allows heat producing control gear to remain outside the barrier and away from insulation, improving control gear life.
• Reduces chance of vermin living on top of insulation hotspots where they may reduce the life of the luminaire, from compacting insulation and or excretion.  This was a common occurrence with Halogen Lighting.
• The heat sink is not exposed outside of the building envelope behaving as an efficient conductor when the luminaire is not turned on.
• Some products are Installable from below the ceiling with control gear.

Insulation-coverable downlights

Fittings that can be covered by insulation (Figure 4) offer several advantages:

• Quick and easy installation.
• Insulation consistency is maintained.
• The heat sink is exposed outside the air barrier envelope but within the thermal insulation barrier in a temperature-uncontrolled loft area. With LEDs off, the heat sink is working against the temperature differential inside and outside.
• Installable from below the ceiling.

Finally

Both solutions for taking care of the building envelope – AS/NZS 5110 and the rare insulation-coverable LED fittings on the market – provide a substantial energy-efficiency benefit as opposed to old halogen recessed lighting.

The latter can contribute to draughts and insulation inconsistencies while also being a fire hazard.

AS/NZS 5110 clearly delineates the task away from the electrical device. It becomes the building envelope and provides the perfect balance of ventilation and energy efficiency for this type of lighting.

Downlights provide light into the living space which means they should be ventilating to that space and not in ‘no man’s land’.

To ensure that an LED with an AS/NZS 5110 barrier – or an insulation-coverable LED fitting – is installed as efficiently as possible, it’s important to put insulation around the luminaire/barrier.

If your customer wants to make the change from halogen to LED for the thermal and airtight barrier improvements, make sure you finish the job and cover the downlights after fit-off.

A saving of $10 per year per downlight can be realised.