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New façade, old buildingA better way for NZ architectsand designers to approach a new façade on a pre-existing commercial project.

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A better way for NZ architects and designers to approach the façade design on a pre-existing commercial project

New Zealand developers are increasingly turning to pre-existing commercial buildings for redevelopment projects, particularly for apartments. This makes sense of course - amid housing crises in cities like Auckland, these projects can be cheaper than starting from scratch, and are an invaluable opportunity to transform heritage buildings to serve a purpose in the modern era yet still pay homage to their former life.

However, changing the façade on a pre-existing commercial build is not a simple task. In many cases, buildings must be stripped bare and reclad, which requires a considerable amount of forethought and a sizeable level of cross-discipline expertise. Even if a façade is not being stripped entirely, small changes in design can still have large impacts on project time, budget and practicality.

This whitepaper is intended as an educational tool for architects engaging in one of these projects. Architects simply cannot know everything, but nor do they need to. In this document you will find ideas on how to approach changing a pre-existing commercial façade, with reference to numerous completed projects from throughout the country.

1 | altuswindows.co.nzHow to approach façade design on a pre-existing building

Part One:

Think first and

plan for practicality.

It’s easy to forget when redesigning a façade that even small changes in size or weight can have drastic implications on future time, budget and practicality. Just a few hundred millimetres extra height on a large sliding door could see the glazing change from 6 millimetres thick to 8 millimetres thick to support wind loads and so on, which has ramifications on its weight and cost. This has a knock-on effect to everyone else involved with that door, including tenants - a heavier door is harder to open, and not everyone will be strong enough.

When recladding a pre-existing commercial building, architects must factor in:

1. Buildability2. Operability3. Replaceability

BuildabilityGetting this right requires collaboration between architects and their various suppliers, to ensure that everyone’s needs are met and a middle ground is found between design aesthetic and the ability to actually realise this design.

Read more about collaboration in part four of this document.

Case study - Hereford Apartments, Auckland: Many of the listed challenges were encountered during Naylor Love’s Hereford Apartments project, which saw a 15-storey commercial building transformed into a 20-storey mixed-use building.

Mike Koot from Vistalite North Harour, who was involved with the project, explained that after consultation with the design team, the height and width of their specified sliding doors - which were 2.6 metres high - was reduced slightly to increase buildability. Even a small reduction decreased the weight exponentially.

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Here are just a few small examples of important buildability factors to consider:

1. Delivery to site: Let’s say you’ve specified the large sliding doors mentioned previously. These over-sized frames are too complicated to be built on-site; they must be manufactured off-site and then delivered whole. In order to get them up to, say, floors 19 or 20, contractors cannot simply throw them on an Alimak (rack and pinion elevator). They must be craned in, which means the build must be geared up with loading frames to accommodate heavy deliveries.

2. Scaffolding: If your windows and doors contractor is trying to get their products in place after scaffolding has been erected around the structure, their entry will be restricted (in part three of this paper, we explore a case study involving this issue). Alternatively, if there is no scaffolding, as is often the case, entry won’t be restricted but contractors will be attempting to install their windows without external access.

3. Partitions: Now consider if your project has had its internal partitions removed, or if the new interior has been implemented already. Internal partitions interrupt the ability of contractors to manoeuvre glazing and door frames from the delivery point to installation point. This means products must be craned on the facing in which they will be installed, which is impractical. It would be faster and more cost effective to deliver all these products at once while the floor is open, and install them prior to partitions going up. But of course this isn’t always possible. Again, a middle ground must be found.

:

OperabilityChiefly, operability refers to the ease with which a building’s occupants will be able to use the space. This is where building performance must be considered prior to designs being drawn up. A 180 kilogram sliding door could provide excellent views and be a unique selling point for your apartments, but that same 180 kilograms represents a significant weight that must be heaved in order to open. You may find that some occupants, older people in particular, may simply be unable to use this feature.

Read more about building performance in part four of this document.

Replaceability It might seem more the property owner’s concern than an architect’s, but replaceability is vital to consider in the early design phases. Should a window break during an apartment’s tenancy, it must be swiftly repaired. However, that means the new glazing must be able to fit in an elevator, or be otherwise easy to transport to the right floor. Again, when size is increased, so too is weight and cost, and while you may be able to work around this during redevelopment, you must also look to the future to ensure that future occupants will be saved the same expense.

How to approach façade design on a pre-existing building

There are many cases around New Zealand where a project redevelopment was designed like-for-like, that is, where a newer version of the same product was installed. It’s understandable why these choices would be made of course - it is cheaper and simpler, after all. However, changing the façade on a pre-existing commercial build is an opportunity to upgrade that same build. While it may cost more at the outset, it can save money in the long run.

For example, the Altus Windows, AllSeasons or Pacific Thermal Suite add additional thermal efficiency over double glazing alone. Specifying these products might change your budget, but it could cut energy costs over the lifetime of the building, and increase thermal comfort for occupants. This can also be used as a selling point when attracting pre-sales before construction.

Architects and designers should be open-minded when undertaking their projects, and seek out cost-effective upgrades that balance an increase in budget or complexity with significant future cost gains.

Case study - Cumberland College, Dunedin: When Brent Griffin from Nulook Morlite was brought on to Dunedin’s Cumberland College redevelopment, his task was to upgrade the façade windows while maintaining the existing heritage look. It may have been tempting to simply replace the old glazing with similar new products, but Brent and the team found a way to improve the design without having to make any structural changes (which would have been difficult considering the frames are steel). Morlite cut the internals out of the window and built a new frame to sit inside it - a frame within a frame, as Brett described. This allowed them to install thermally broken frames with double glazing, increasing the performance of the building while retaining its look.

“There were existing steel frames and we cut the internals out of the window and built a new frame to sit inside it - a frame within a frame.” - Brent Griffin


Part Two:

Take the opportunity

to make upgardes.



The worst thing you can do on a façade redevelopment project is leave it too late. Working out the details as early as possible is something that is often missing from New Zealand façade design. But there are important questions that must be asked at these opening stages: How are you going to install the window system? Is it a curtain wall, hanging off the side of the building, or slab-to-slab? How will this be accessed, be it cranes, scaffolding or something else? Has weathertightness, fire protection and acoustic performance been factored, and importantly, do all of these elements integrate into the main aesthetic?

This plays into the buildability elements we spoke about in part one. It’s never too early to talk to a façade engineer, or to talk to the Altus Windows architectural team to figure out the practical details of installing new windows and doors on a pre-existing build.

What are the risks of leaving it too late?1. Increased budget as complications arise, such

as when contractors discover access issues.2. You may purchase costly products that weren’t

necessary - for instance, high-performance glazing on a façade that didn’t require it.

3. Future tenants might not get the full benefit, where either they can’t operate certain doors or where something like incorrect glazing creates discomfort on certain sides of the building.

Case study - Mellor Laboratories, Dunedin: Buildability was going to be an issue for the Morlite team on the University of Otago’s Mellor Lab project. Brent Griffin was working with window spans 3.6 metres wide and 8 metres high. Getting these to site and then craning them into place behind the scaffold was going to be a huge challenge. However, the project was planned to take part in two halves, so that the building could continue to operate even while construction was underway. This allowed Brent and Morlite a chance to test a method to get these spans in place, and then use this to make the second stage of the project even more efficient.

Working out the details as early as possible is something that is often missing from New Zealand façade design - so act early.

Part Three:

Tackle the façade as

early as possible.



Architects are expected to know a lot, but it’s important to recognise that if you aren’t an expert in a particular field, it’s better to collaborate than to go it alone. After all, you wouldn’t expect your local GP to know everything, but rather for them to diagnose an issue and refer you to the relevant specialist. Architects should operate in the same way.

In New Zealand, there are two specialist fields that we often overlook in the early stages of design.

1. Façade engineersNew Zealanders often don’t bring in their façade engineers early enough. However, talking to this specialist earlier can help eliminate some of the guesswork from the design and prevent having to revise certain details later on, which you thought were set.

For instance, a big one is the difference between basic wind calculations and factored wind calculations. Applying assumed numbers to basic wind factors is certainly faster, but when the façade engineer is brought in later and performs a full analysis closer to lodging building consent, the new numbers may be more or less than the initial estimate. In this case, details must suddenly change and the project is delayed.

Working out the details as early as possible is something that is often missing from New Zealand façade design - so act early.

Part Four:

Collaborate with others

to find the best solutions.

Case study - Wellington City Council, Central Park, Wellington: This project required updating a 1960s apartment block to make it healthier, safer and more secure. By the time Nebulite’s Tim Morgan began discussions on how to install new windows into the structure’s existing openings, a façade engineer had already supervised putting a water coating system around the concrete, which allowed Nebulite’s windows to have greater sealing properties to prevent leaking (a key objective).



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2. Building performance engineersA building performance engineer’s focus is on ensuring that a building will work for the people who will own and use it, and can operate well within its environment. They use scientific and computational models combined with industry experience to give decision making guidance; they explain how certain elements will impact other elements and liaise with your other specialists (e.g. façade engineer, acoustician) to find an integrated solution that will work for everyone.

Specifically with façades, building performance engineers are experts in glazing, an area many have some knowledge but few have expertise. By modelling and testing various glazing scenarios, building performance engineers can help you specify window products that will increase efficiency and save money.

The best way to tackle changing the façade on a pre-existing commercial build is to do so collaboratively. When architects and designers take an extra moment to discuss their project with experts in the various fields required, be it engineers or window suppliers they will be given a raft of evidence- and experience-based data to be able to more strategically specify designs. This must also be done as early as possible, so that any changes in plan won’t drastically affect future cost or time.

To speak more with an expert on window and door systems, contact Altus Windows today.

Case study - InsideOut: In one recent project, Ruth Williams from building performance specialist InsideOut was called in to assess an apartment building that was getting a new curtain wall façade all the way around - a lot of glazing to be changed. The original designs had planned for low-E double glazing, however simulation evidence suggested that, based on building orientation and the sheer quantity required, the extra cost wasn’t justified on the basis of thermal comfort and energy efficiency. Most of the summer heat was going to come from sunshine, which would then become trapped, causing the building to overheat. This would encourage tenants to use air conditioning, driving up energy costs and mitigating any gains the windows would have brought in winter. Clear double glazing would not cause the same problem and offered a cost saving


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