Direct Gain

8/11/2019 Direct Gain

1/19

Building

Science3

B

BUILDING SCIENCE 3B

Lecture 3: Passive Solar Design

DIRECT SOLAR GAIN

Lawrence Ogunsanya

[email protected]


2/19

Direct gain Design Overview

Sunlight incident on transparent surfaces allows the energy to enterthe living space directly and is called Direct Gain.

Direct Gain systems are designed primarily for heating. In a direct

gain system, the collection, absorption, and storage of solar energy

occur directly within the living space.

The aim of the designer is normally to maximise solar gain within

the building in the winter (to reduce space heating demand), and to

control it in summer (to minimise cooling requirements).

The system can also be used to even out the fluctuations during the

day, and to some extent between days.

During the winter, sunlight enters the living space through the north

facing faade/glazing. The solar radiation is in turn absorbed by

elements in the interior space. (e.g. floor, walls, ceiling and

furnishings)


3/19

Direct Gain Design Overview

During the summer, the north facades should be well shaded to

prevent excessive solar heat gain.

Shading elements, such as overhangs can be an effective device to

achieve this.

Therefore, North facing windows thus form the basis for the simplesttype of solar heating system.

With some simple guidelines, this design is the cheapest and best

way to incorporate solar into a house.

Surfaces should be generally facing North (to within 20-23 degrees)

Overhangs should prevent unwanted summer gains. (it should be

minimum of meter long)

Window area should be 8-12% of the house floor area if no extra

thermal mass is added


4/19

Direct Gain Passive Solar Design

Excess window area can result in a loss of privacy, too much

glare, under heating and overheating

This amount of passive solar gain should provide no more than

40-50% of the yearly heating load


5/19

Direct Gain Passive Solar Design

Direct solar is applied through

the following:

Collectors

Storage

Control


6/19

The principal function of a direct gain collector is to admit andtrap solar energy so that it can be absorbed and stored by

elements within the direct gain space.

There are three basic types of direct gain collectors: solar

windows, clerestories, and skylights.

Direct Gain Collectors


7/19

Solar window A solar window is simply a standard, off-the-shelf window or

patio door Installed on the north facade using conventional

construction methods.

The collector frame can be wood or metal and should be wellcaulked (sealed) and weather stripped.

The solar window can be vertical, or it can be slightly tilted to

maximize the amount of incoming solar radiation.

Double glazing is recommended standard for the windows,

However high performance glazing with low-e coatings, gas

fills (triple pane) are better but expensive.



8/19

Double Glazing Triple Glazing



9/19

Clerestories

Clerestories serve the same function as solar windows. They

also allow light to penetrate deeper into a space better than

solar windows , often enabling direct sunlight to strike the

south wall of the space.

As in solar windows, clerestories can be vertical or tilted,using the same type of recommended glazing.

Clerestories can be used together in a sawtooth pattern In

order to increase the total amount of solar radiation entering

a building


Sawtooth Glazing


10/19


11/19

Skylights Skylights serve the same function as the other direct gain

collectors and can be placed flat on flat roof or tilted In a

south/north facing sloped roof. Skylights are often the least

effective collector type.

The collective character can be improved with a reflector.


Skylight with reflector


12/19


13/19

Direct solar gain control systems can be achieved throughshading, reflecting and insulating.

Shading

To avoid excessive heat gain in the summer, it is

recommended that you provide shading for the direct gain

collector.

The most thermally effective shading devices are those

placed on the exterior of the home, such as simple overhangs

(fixed or adjustable), pergolas, vegetation, awnings, and

louvers Interior shading devices include roller shades, blinds, curtains

and movable panels.

Interior shading devices provide insulation for the interior

space.

Direct Gain Control


14/19

Direct Gain Control
http://www.google.com/url?sa=i&source=images&cd=&cad=rja&docid=J7HqMXuktdwC-M&tbnid=lcRhvHM-gOQGoM:&ved=0CAgQjRwwAA&url=http%3A%2F%2Fwww.muracaent.com%2Fawnings.html&ei=XowmUvrDL5CUhQf4_oGACw&psig=AFQjCNH9_ylXsHcbUV6Ki1uYW82nPaK8Bg&ust=1378344414873993


15/19

Reflecting

Reflectors placed strategically above or below a collector canhelp increase overall system performance.

The provision of reflectors can also improve solar collection

by 30% to 40%.

Light coloured landscape elements such as patios or terracesare recommended. It is noted , that these elements are not

as effective as reflector panels. However, they do not present

glare and they require no additional maintenance.

Direct Gain Control


16/19

Insulating

Direct gain storage ceiling ,wall and floors that are exposedshould be insulated externally and internally to reduce heat

loss and absorb excessive heat.

Direct Gain Control
http://www.google.com/url?sa=i&source=images&cd=&cad=rja&docid=XxyOq-rV3_fllM&tbnid=Zpq6PxjroO5loM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.esi.info%2Fdetail.cfm%2FKnauf-Insulation%2FTf04-Timber-frame-walls%2F_%2FR-30299_WA103NS&ei=7dAmUuKrE4rI0AXBqIC4Ag&psig=AFQjCNFrLYtHicdJalf_Kljmlf8HS--Sqg&ust=1378361882067525


17/19

Direct Gain Control
http://www.google.com/url?sa=i&source=images&cd=&cad=rja&docid=LGBQfZpdge5mrM&tbnid=sehjHvKMuyaaXM:&ved=0CAgQjRwwADioAg&url=http%3A%2F%2Fwww.bisinsulation.co.uk%2Fexternal-wall-insulation%2F&ei=GdImUrmfI7KP7AbR44DQCQ&psig=AFQjCNEMUlSijUndiSMZacZo07L4QKniEA&ust=1378362265652734


18/19

Advantages

Direct gain can be the easiest to build using standard

construction materials and methods

The system dose not radically alter the appearance of the

home

The system provides effective natural light and reduces energy

consumption.

Improves the comfort of the interior space.

Disadvantages Large expanse of north facing glazing can cause glare and

privacy problems

Ultraviolet radiation in sunlight can fade and degrade fabrics

Some high performance devices can be costly.

Direct Gain : Advantage and

Disadvantages


19/19

Questions

Direct Gain

Documents

Transcript of Direct Gain