We are currently going through the process of designing a small house for a section facing towards the north-east. An important part of the design process is determining where to place living areas, bedrooms and bathrooms. As well as taking advantage of the best views and practicality of living, it is also important to take into account of the free energy provided by the sun.

On clear winter days, the sun can send around 500 Watts of heat through each square metre of unshaded north-facing window. Therefore it makes sense to have your biggest windows facing north and your smallest on the south side.

Once you have winter sun streaming through your north facing windows it is important to consider the materials used in the house and how the capture and hold heat i.e what is their thermal mass.

Thermal mass

Thermal mass is a term used to describe solid materials that absorb heat, store it up and release it when temperatures drop. Generally the thicker and more dense a material is, the better thermal mass properties it contains.

Rooms that get direct sunlight in winter, adding or exposing existing thermal mass will make better use of free heat from the sun.

  • If you have an insulated concrete floor slab – consider exposing it (you can polish, paint or tile it) where it gets direct sun.

In summer, the opposite applies. During summer the sun is higher in the sky. A simple rule of thumb is to place thermal mass where it gets direct sun in winter and shade in summer.

Eaves that over hang your windows protect the thermal mass from direct sun during the hottest part of the day. Shade lets the mass remain nice and cool.

A home designed to harness the sun’s free warmth:

  • is placed on the sunniest part of the section – to access the most sun
  • is oriented to face the sun – with main living areas facing north and service areas (garages, toilets) facing south
  • has plenty of insulation – to trap in the free heat from the sun
  • uses thermal mass – like concrete floors or brick walls exposed to the sun
  • has appropriately sized and positioned windows – moderately large on the north-facing side of the house, smaller on the east and west sides, and smallest on the south side
  • has properly designed overhangs over northerly windows to limit summer sun whilst allowing plenty of sun in during winter. Overhangs don’t work well on east and west sides as the sun is too low. Deciduous trees and movable shades or louvers are better options here.


The same concepts apply when you are renovating your home as when you are designing from new. Using simple techniques you can harness the suns free energy to help heat your home. Eg. take advantage of having tradesman in you home to upgrade insulation in the walls.

Thoughts to consider when renovating your home

  • Add/upgrade windows on the northern face of your home.
  • Upgrade all window frames and glazing
  • Focus on issues causing home dampness
  • Cut down trees and bush blocking northern sun
  • Remove existing wall linings and upgrade insulation
  • Consider using materials with good thermal mass properties

For more information on combatting home dampness check out – Keys to a dry and healthy home

Simple techniques and good design will cut your home’s heating and energy needs.

Credit: https://www.energywise.govt.nz/at-home/building/