A little drama of windows

Last week, I was working on NatHERS and BASIX for a residential building in Sydney City.

Well, a little drama with the architect happened.

Here are some emails between us.

I've seen a number of architects. Their most important concern is aesthetics, or in other words, the appearance of "their" building.

"Sustainability"? They don't care!

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From: Dont Sustain
Sent: Thursday, 20 March 2008
To: FireStallion; Loss Energy
Cc: Sudden Jump; Minimum Spend; Go Froth
Subject: RE: BASIX certification on Site X

FS Comments in red

Regards Dont Sustain Associate Director | nom. Architect xxxx 0402 xxx xxx

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From: FireStallion

Sent: Thursday, 20 March 2008

To: Dont Sustain; Loss Energy
Cc: 'Sudden Jump'; 'Minimum Spend'; 'Go Forth'
Subject: RE: BASIX certification on Site X

Dont and Loss

I’ve worked on some different options to get the north east corner apt of level 12-17 under the cooling allowance 64.7

• Option A – Louvres to all glazings – 76.8 Failed
• Option B – As option A but with window height of B2, B3 changed to 1.6m – 66.1 Failed
• Option C – Double glazing to all glazings with external blinds to Terrace, B2 & B3 – 76.1 Failed
• Option D – Different double glazing with B2 & B3 external blinds, type 1523 (6mm super grey/6mm air/4mm Energy advantage Low-E, U=2.552, SHGC=0.157) – 27.6 passed What double glazing is proposed for the northern windows….ie the main curtain wall? I would prefer not to commit to external blinds. As this is only morning sun to the east to B2 and B3 I am surprised it makes such a difference.
• Option E – As option D but using double glazing type 657 (5mm SuperGrey/13mm air/4mm clear, U=4.112, SHGC 0.203) – 44.8 passed Is this just the glass to the B2 and B3 or to the full north?
• Option F – As option E but with no external blind to B2 & B3 – 47.4 passed

And as a sensitivity comparison, residence 2 is also compared with different options, cooling allowance 64.8:

• Option A – as SC layout with B1, B2 & B3 external blinds – 59.9 passed
• Option B – as option A but with no external blinds – 80.1 failed
• Option C – as option A but with blinds to all glazing – 45.8 passed If we pass without external blinds then that’s great news. Means at least the client does not need to commit as yet on this western terrace

From the above results, I have the following remarks:

• The SHGC (Solar Heat Gain Coefficient) of the proposed glass is critical to keep the cooling load down other than shading devices. SHGC should be kept under 0.3 or lower. Double or single glazing, which affects the U-value, is not as critical. However, glazing with low SHGC tends to be dark and may not have good visual effects. Reflectivity and transmission data is not available at the moment to check if they comply with DCP or not. When you meet with Pilkington, check the SHGC’s (under 0.3) and the reflectivities (under 20%) to shortlist eligible glass types. Yes…dark glass is a problem. Will discuss at meeting
• External blinds, or other forms of shading, have a very significant impact on the cooling. In many cases, the shading can make or break the BASIX allowances. [For comparison, direct solar radiation through reference glass can be up to 550 W/m2* where diffuse (shaded) solar radiation can get down to 40 W/m2*. That’s a 1275% difference. Even very good and sophisticated glazing can’t beat a simple overhang. * From p.43 of Carrier System Design Manual Part 1]

FS – I think you should come to the Pilkington meeting please. Will send the invite

If you have any questions, please contact me.

Regards

FireStallion

Accredited ABGR Assessor, GBCA (Green Star) Accredited Professional

Email: firestallion100@gmail.com

-----Original Message-----
From: Dont Sustain

Sent: Monday, 10 March 2008

To: FireStallion; Loss Energy
Cc: Sudden Jump; Minimum Spend; Go Forth
Subject: RE: BASIX certification on Site X

FireStallion

Comments below.

For the moment, the typical 4 apt floors are modelled as per your proposed glazing allocation. It appears apt 1 has some issues to get pass BASIX as its cooling load is “very” significant. This is because the height of the windows are assumed to be as high as possible and for the Living and Family Rooms glazing, no shading is available.

Windows are typically at 2800 head. Yes there is a lot of glass….but this is the premium view so we will not be reducing extent of glass. The main glazing to the north is double glazed so this reducing cooling load significantly. The remaining glass to the east then is proposed as single glazed. We seek your advice on whether we need to extend extent of double glazing…but would prefer high performance single glass as first port of call.

One point to be bear in mind is that: although the remaining three apts pass the BASIX cooling and heating requirements, it is recommended that each apt should improve its thermal performance to around 5 stars to get better results towards achieving a 5 star Green Star Residential rating. Also note that the weighted average cooling requirement of all apts is 46.4. There is a (remote) possibility that all apts pass their required heating and cooling requirements but the weighted average requirements cannot be met.

Here are some suggestions to improve the apts’ thermal performances:

· Reduce glazing areas, esp. apt 1 will require some rationalising of the glazing areas to get pass BASIX. An empirical value for glazing to floor area ratio is 35% or below (with good shading available), esp. if 5 stars NatHERS is to be achieved. Apt 1 has a glazing to floor area ratio of 52%. Can’t reduce glazing…The amazing view is what is selling these apartments. Northern glass is double glazing. Do we need to extend extent of double glazing.

· Provide shading, set backs and /or light shelves to windows. This is mandatory to claim cross ventilation bonus in BASIX. (Note that the louvred screens are very effective in reducing the solar heat gain for the western façade glazing.) I am confused….how is shading mandatory for cross ventilation bonus…and with high glazing…why are light shelves required….when the higher glazing means more light ingress.

The main western window as per original markup is double glazed with no external shading. Same scenario as the DA.

Likewise the single glass to the terrace stacking is set back within the terrace zone and overhang. Same scenario again as the DA.

We can introduce some external glazed roller blinds or equal to the western windows that are set back from the terrace line if needed…but we are loath to add additional louvred screens. For memory we went through the same debate for the DA.

· Use alternative glazing types. Currently, the selected glazing types have very good thermal performances – single glazing with U = 3.855 and SHGC = 0.466 and double glazing with U=2.255 and SHGC = 0.407.

· We seek your advice here. At DA stage you provided us with a list of glass options with general performance.

I propose a meeting on Thursday afternoon at our office to discuss. Can you confirm your availability.

Sudden- would you be free – say Thurs 4pm on your way home???

Can you send us the proposed elevations for fine tuning the NatHERS calculations?

Loss will send through

Regards Dont Sustain Associate Director | nom. Architect xxxx

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My "philosophy" will be somehow different to the above.

If you have a magnificent view, why don't you be part of it?

It's the connection with the environment that I am speaking of.

Modern life separate us from our environment. If you have a good view, then go to the balcony and be part of it. Fell the breeze, smell the scent, hear the sound! Don't just look at the view!

Well, there is a fundamental difference in philosophy anyway.

With the client on the architects side, it looks like the unsustainable option of providing view with "better" glazing will prevail, rather than a simple sustainable alternative.

What cost is "Sustainability"?