Week 8: Thermal Loads

What sort of windows should be used? How do we effectively incorporate shading for a building? What are best practices for insulation and ventilation?

Lecture 1: Shading and Facade Design

Slides are here.

Static shading. Something you attach to the building outside the window. Can avoid visual discomfort. Avoid thermal discomfort. Avoid cooling loads. Downsides: obstruct your view, losing out on valuable solar gains in the winter.

Basic guidelines for designing static shading system

• Use horizontal shading systems (blinds, overhangs) for equator-facing windows. Horizontal elements effectively block vertical surfaces when sun is high.
• Use vertical shading systems for east-west facing windows. They block low solar altitudes which may trigger glare and overheating during summer.
• Facades facing away from the equator generally don't require static shading. Direct sunlight is rarely incident.

Of course, we can combine overhangs and fins. This kind of design is ideal for simulations. Can also change scale.

That icon New York Times photo with their logo across blinds on the front of their building is actually interesting now.

Iconic shading book from the 1950s: Solar Control and Shading Devices - Olgyay and Olgyay

Main tasks in designing: 1) When is it desireable to have solar gains on my window? (start and end date, start and end time of day) 2) What form should a device have to fulfill 1).

Aqua building in Chicago. Very interesting.

Shaderade. A DIVA algorithm for designing a shading system. Lets you generate free form shapes like the Aqua building, but also know that they are performative. Can optimize for different things, e.g. reduce sum of heating/cooling load, or reduce carbon use.

Lecture 2: Ventilation

Slides are here.

Ventilation: purposeful or accidental movement of air inside and outside buildings.

10-15% of the air in an office buildings has to be fresh.

How much fresh air does a person need? 10 litres per second. This is for breathing but also takes into account off gassing of materials, etc. If you drop below you get "sick building syndrome". (15 ft^3/minute)

Air Exchanges Per Hour (ACH): The number of times all air in a building is exchanged with outside air over the course of an hour.

How do you measure the infiltration rate of a building? Blower door test. Close all windows, have building as tight as possible, install a fan to blow air out of the building and create a negative pressure. At that point you can e.g. take a candle around all the cracks to look for where it grows stronger. Can also take more formal measurements. Measured in cfm50.

CIBSE is the UK equivalent of ASHRAE.

Why are we excited about natural ventilation? It's free. It's more "architectural". ("Other wise you have to leave things to the HVAC engineer, with sometimes disastrous results") Reduces energy usage.