In Sefaira's latest white paper, our engineers have put 4 commonly used rules of thumb to the test to see how they really score for green building design. Architects seeking to design buildings with high energy performance have commonly relied on rules of thumb. While these are useful they can be misleading and in many cases won't help optimise a design, considering the many interacting elements of efficiency. Click through to download the white paper!

1. Four Rules of Thumb
That Could Lead You Astray
Rules of Thumb can point you in the wrong direction. Here’s what you need to know so you don’t get
misled.

2. 4 Rules of Thumb That Could Lead You Astray
Why do rules of thumb fail?
• They don't take into account the
specifics of the site and building design
• They don't apply equally well to all
building types
• They don't help you understand what's
important, and can draw attention to
the wrong parts of a design
We looked at 4 rules of thumb related to
the building envelope, and found that they
can often point in the wrong direction.
Rules of Thumb

3. 4 Rules of Thumb That Could Lead You Astray
Rule No. 1: The ideal
alignment of buildings is for the
longest axis to run East-West
The rule works with a simple
rectangular building. But what
happens with more complex
geometry and shading from
surrounding buildings?

4. Rule No. 2: Shading Depth
4 Rules of Thumb That Could Lead You Astray
Shading devices are tricky, even
for rules of thumb: rules can
work well for buildings that are
externally loaded, south-aligned,
and built to standard
specifications.
But what happens if we specify a
high performance envelope? Do
the standard depths still apply?

5. Rule No. 3: Glazing Ratios
4 Rules of Thumb That Could Lead You Astray
Glazing ratios are intended to optimize solar heat gain,
with different rules for different climate zones.
This is an important consideration … but what is the
effect of different glazing types or different shading
strategies? Do the rules still work?

6. Rule No. 4: Natural Ventilation
4 Rules of Thumb That Could Lead You Astray
A standard rule of thumb for
natural ventilation states that the
ideal operable window area is 5%
of the total floor area to be
naturally ventilated.
Does this % stay the same for
different levels of insulation,
shading, and thermal mass? And
is it enough to maintain occupant
comfort?

7. 4 Rules of Thumb That Could Lead You Astray
What’s the best orientation for this office building in Pittsburgh,
PA? Which option minimizes energy use?
Putting Rules of Thumb to the Test
A B C

8. Download the full white paper to see
whether your guess was right!
The Sefaira white paper discusses in
detail the four rules of thumb presented
here. Follow the link below to discover
the many cases where rules of thumb go
wrong, and explore ways to put them
right again!
Sefaira’s White Paper
Contact Details
marketing@sefaira.com | www.sefaira.com
4 Rules of Thumb That Could Lead You Astray