Rational design leads to cost saving on refurbishment project

by Darren
Rational design leads

Following a rational approach enabled the professional team working on the refurbishment of the East Rand Galleria to channel saved funds sensibly.


The 45 000m² East Rand Galleria in Boksburg, to be rebranded East Point, is currently undergoing a R411-million reconfiguration and renovation, which includes the replacement of the entire roof and all the insulation. Walls & Roofs investigated how a rational design approach has impacted this project.

Not only did a rational design approach dictate a significant saving on the amount of insulation required for East Point, but in doing so, it enabled the developer and owner, SA Corporate Real Estate Fund, to direct capital expenditure to other areas where it made a bigger difference in getting the best energy return for the whole building.

According to the architect, Jeffrey Cole, the problem arose from a technical challenge faced by the professional team. “In preparing the feasibility for the project, the project Quantity Surveyor had allowed for 135mm thick fibreglass wool type insulation as per the deemed-to-satisfy compliance of SANS 10400XA. What had not been allowed for was the additional structure required to support the roof sheeting over the 135mm insulation without compressing such, and thereby negatively affecting its performance,” Cole states.

“The only option left to the team was to look at board type insulation, but the cost of compliant, deemed-to-satisfy, 80mm Lambdaboard® was again beyond the budget constraints of the project. The only solution was to undertake a rational design on the building in order to reduce the thickness of insulation required and thereby the cost,” he explains.

Deemed to satisfy vs rational design
Regulation XA and supporting standard SANS 10400XA for energy usage in buildings allows for various routes for compliance.

“While you are spending money on XA compliance, you need to make sure that you get the most bang for your buck,” states Howard Harris, director at energy and sustainability consultancy, Structatherm Projects, who was commissioned to do the rational design. “Other than the fact that you compromise on heat bridges over purlin where bulk insulation is compressed, in this case it also presented serious fitting challenges,” he says.

He further explains that as insulation is added to obtain the required thickness of 135mm, at a point one starts to get marginal returns since the first 60mm, for argument’s sake, does 80% of the job, with the next 20mm taking it up to 90%, the next 20mm perhaps bringing it up to 95%, with the rest contributing virtually nothing.

Harris calculated that by using Rigifoam’s Lambdaboard® insulation, only 50mm across the entire mall would be necessary to comply. This was later adjusted to 60mm to accommodate the reuse of the three existing chillers at the mall in order to save initial capital expenditure.

According to Ashley Underwood, mechanical engineer at Aurecon, they came to the final thickness of 60mm after having calculated that it was the minimum roof insulation that would allow them to reuse the existing chillers and still achieve the HVAC load. “So from an energy point of view, the insulation is actually better than it needed to be,” he comments.

Savings channelled optimally
The extra money that became available due to the saving on insulation was spent on implementing a more efficient HVAC system. A full airside economy cycle was added to all air handling units to enable free cooling whenever it is available.

“Basically, the system uses the outdoor air to condition the building whenever the outside temperature is cooler than on the inside of the building, which is pretty often in Johannesburg,” Underwood explains. “This free cooling will result in a more significant energy savings than what a thicker insulation board would have achieved, and both the building owner and the tenants will benefit.”

Traditionally, Underwood says that 40mm Lambdaboard® over purlin is sufficient insulation for buildings before the cost of adding thickness starts to outweigh the marginal gains in energy-efficiency. The 40mm insulation is important to lower internal surface temperatures and enhance thermal comfort; when applying a full life cycle cost analysis many other energy saving strategies, such as air side economy cycles, have a much shorter payback period than increasing the roof insulation.

Calculating real costs
“Although the bulk insulation is cheaper, the construction details are significantly more complicated, when analysing it properly, taking into account that the fibreglass would have been squashed over the purlins, lowering the average thickness, together with the spacing challenges that would have required additional reinforcement, labour cost and time, it is unlikely that the deemed to satisfy fibreglass insulation option would have been much cheaper. Lambdaboard® no doubt made more sense,” he says.

James Powell from Rigifoam also points out that with Lambdaboard®, the long-term thermal values will last the lifespan of the building, compared to bulk insulation that accumulates dust and collapses over time, causing HVAC systems to work increasingly harder and costs to increase.

Installation challenges
Being a reconfiguration and renovation project, the use of the existing building shell has proved to be a big challenge. As the mall has grown over the years, the various expansions weren’t consistent, resulting in uneven purlin spacing. This meant that the roofing contractor had to lift the roof sheeting off, measure the purlin spacing and cut the Lambdaboard® to size before starting with the installation. In effect, it is like a jigsaw puzzle using customised cuts of Lambdaboard®.

“Facing this challenge, the benefit of Lambdaboard® is its expanding capabilities,” says Powell. “Although we prefer to stay close to 2m, on a 60mm board you could go as far as 2,5m, while bulk insulation would have been much more difficult to manoeuvre.”

Preferred material
One of the major tenants in the mall, Pick n Pay, has used Rigifoam’s Lambdaboard® in several other store developments, specifying the product as a standard for the past two years. Because it is a rigid board, it nullifies the need to install a separate ceiling, perfect since Pick n Pay has an exposed ceiling.

“Apart from being environmentally friendly and providing insulation, Lambdaboard® is also an aesthetically appealing solution,” says Ponen Rajah, Pick n Pay’s general manager for store design and construction. “It looks neat and the white colour, as opposed to the traditional foil, reflects light back and reduces the demand for artificial lighting. The Pick n Pay installation is washable and can therefore also be wiped clean from time to time.”

According to Underwood, there is definitely a strong focus from developers to ensure optimal energy-efficiency in their buildings. “Developers now realise that they too will reap the benefits and therefore consider long-term financial models rather than just building and selling, with the Green Building Council of South Africa’s As-built rating tool definitely being a catalyst for this.”

Tel: (011) 421 0313
Website: www.rigifoam.com

Key benefits of Lambdaboard®
The product:
–    Is recyclable.
–    Is an environmental “green” choice.
–    Contains no ozone-depleting substances.
–    Is HCFC-free.
–    Has the highest stable R-value per 25mm of thickness.
–    Is moisture-resistant and water-repellent.
–    Is resistant to solvents used in construction adhesives.
–    Has excellent dimensional stability.
–    Has superior performance in fire tests.
–    Doesn’t soften at 60°C.
–    Has a stable service temperature range from -30°C to 140°C.
–    Is made from thermo-set material that does not soften or melt.
–    Has a high compressive strength.

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