Impact of Ceiling Height on Building’s Energy Demand

In this parametric study, we have developed a simple Reference Building (click here to see all modelling details for different climate zones) with thermal build and added insulation following NCC Deemed to Satisfy requirements. While keeping Total R-values and window thermal performance values similar to the NCC minimum requirements, we investigate the impact of increasing the ceiling height from 2.4m to 3.5m on the building’s heating and cooling demand. DesignBuilder is used for the purpose of this analysis.

Daylight Autonomy

Key points of this article

  • High ceiling in hot climate zones have little impact on the cooling demand of the building. It is almost neglectable in Climate zone 2.

  • In cold climates, high ceilings should be avoided. In those climates, heating demand tightly depends on the height of the ceiling in a non-linear fashion.

  • High ceiling elevates daylight access and makes you feel spacious and luxurious, but buildings with high ceilings are costly to build, heat and cool.

  • The standard ceiling according to Australia’s building code is 2400mm high but the most common ceilings in the market are 2550mm or 2700mm high.

  • Increasing ceiling height affects thermal demand the most in climate zones 6, 7 and 8.
    Referring to the following graph, in Melbourne’s climate zone 6, increasing the ceiling height from 2.4m to 3.0m (which is a 0.6m or 60cm increase) results in a significant 12% increase in the building’s annual heating and cooling demand.

energy assessment, VURB, JV3, NCC, Energy efficiency, Green Star, NatHERS, NABERS, DTS, Deemed to Satisfy, Daylight modelling, Alternative solution, Performance Solution

High ceilings, benefits and downsides

It is not a secret to a person who lived in different houses that the height of the ceiling, emerges one’s sense of belonging to a living space. Picture a luxury home, and many can bet on your imaginary home to have high raked ceilings and lots of windows. This image of a luxury home, certainly resonates more with us Aussies, since we prefer everything to be big! Well, not always big things are the best and big things generally come at a great cost. The following section summarizes pros and cons of having high ceilings in a new-built houses:

Pros
Cons
  • Daylight access
    High ceilings allow more daylight to enter a room. Living rooms with large floor areas generally require high ceilings for the natural light to reach the deep and far parts of the living room. With large ceilings, it is possible to have high windows that aside from the daylight access, allow a vast field of view to the outdoors. High clerestory windows are proven to be very effective in reducing the building heating demand in cold climates.

  • More Spacious
    A high ceiling makes a small space look big! the more space you have the more you feel a sense of belonging to the space. High ceilings allow for the installation of chandeliers, large paintings and feature lighting.

  • Added value
    High ceilings are luxuries and the extra volume and wall area, allow more design features to be implemented. Aesthetics grab the attention of buyers and in the construction business, nothing generates positive impulses the same as a generous living space!

  • Cost of heating and cooling
    Perhaps the biggest downside of high ceiling is the extra cost you need pay to heat the bigger space in winter and to cool it down in summer. Warm air accumulates at the highest part of the ceiling and makes the distribution of warm air difficult in winter. Unless you have the radiant floor heating or ceiling fan to circulate the air, aside from the high cost of living, your thermal comfort could be impaled.

  • Maintenance
    Cleaning the high parts of walls is both difficult and unsafe, therefore, cleaning or repainting the walls requires a contractor. The higher the ceiling, the more expensive to undertake maintenance.

  • Building cost
    Buildings with high ceilings and especially, with high raked ceilings cost more to build. Though the added value of a high ceiling could compensate for he high construction costs later, high costs buildings are not as easy to sell as the buildings with moderate costs in the market.

Ceiling height thermal energy demand VURB JV3 DTS NatHERS Green Star Performance Solution

What is the standard ceiling height in Australia?

National Construction Code (NCC) Volume 1, Part F3.1 prescribes minimum ceiling height for different space types. This is considered a “Standard” ceiling, and ceiling height above this minimum value is considered a “High” ceiling.

Class 1, Class 2 and Class 9c
Class  5, Class 6, Class 7 and Class 8

Habitable spaces excluding Kitchen – 2.4m
All other spaces including Kitchen – 2.1m

All spaces – 2.4m
Corridor, pathways or the like – 2.1m

Class 9a and Class 9b
Any building

Class 9a –
operating theatre or delivery room – 3.0m
All other health-care related spaces – 2.4m
Class 9b –
School, assembly buildings or corridors for accommodation of < 100ppl – 2.4m
Assembly buildings or corridors for accommodation of > 100 people – 2.7m

Airlock, pantry, store, garage, sanitary compartments other than accessible change rooms – 2.1m
Commercial Kitchen – 2.4m
Above a stairway, ramp, or the like — 2 m measured vertically above the nosing line of stairway treads or the floor surface of the ramp, or the like
Accessible adult change facility — 2.4 m

Reference Building Sensitivity Analysis:
Impact of Ceiling Height on Thermal Energy Demand

The following section details the characteristics of NCC Reference Building with ceiling height as a variable in this analysis.

Ceiling height energy demand VURB JV3 DTS Green Star NatHERS NCC BCA energy efficiency performance solution
General Reference Building Characteristics
Roof: Pitched roof (23 degrees) with solar absorptance of 0.6.
Ceiling: varies between 2.4m to 3.5m, 10 mm plasterboard ceiling.
Roof and ceiling insulation: In accordance with NCC Vol 2.0, Part 3.12.1.2.
Roof lights: No roof light, unless required by NCC Vol 2.0, Part 3.8.4.
External walls: 110mm masonry veneer with a solar absorptance of 0.6.
Wall insulation: The min Total R-Value specified in NCC Vol 2.0 Part 3.12.1.4.
Internal walls: 70 mm timber frame with 10 mm internal plaster lining.
Ground floor: Concrete slab-on-ground, insulated under NCC Vol 2.0 Part 3.12.1.5.
Glazing: In accordance with NCC Vol 2.0 Part 3.12.2 or Glazing Calculator.
Air movement: In accordance with NCC Vol 2.0 Part 3.12.4.
0.6 ACH infiltration allowed all the time.
Artificial lighting: In accordance with the max illumination power density allowed by NCC Vol 2.0 Part 3.12.5.5 without any device control measures.
Internal heat gains: 5 W/m2 averaged over 24 hours.

For the purpose of this sensitivity analysis, ceiling height varies from 2.4m (reference value) to 3.5m for all climate zones.
Refer below for the outcomes of thermal modelling for each climate zone:

NCC Climate zone VURB
Climate Zone 1
NCC Climate zone VURB
Climate Zone 2
NCC climate zone 1 thermal modelling VURB
NCC Climate zone 2 VURB thermal modelling

Climate type:
Example city:
Weather file name:
Annual heating demand:
Annual cooling demand:
Total thermal demand:

Hot humid summer, warm winter
Cairns, QLD
AUS_QLD_Cairns.Intl.AP.942870_TMYx.2007-2021
Not significant – not required by the NCC
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m

Climate type:
Example city:
Weather file name:
Annual heating demand:
Annual cooling demand:
Total thermal demand:

Warm humid summer, mild winter
Brisbane, QLD
AUS_QLD_Brisbane.945760_TMYx.2007-2021
Not significant – not required by the NCC
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m

NCC Climate zone 3 VURB
Climate Zone 3
NCC Climate zone 4 VURB
Climate Zone 4
NCC Climate zone 3 VURB thermal modelling
NCC Climate zone 4 VURB thermal modelling

Climate type:
Example city:
Weather file name:
Annual heating demand:
Annual cooling demand:
Total thermal demand:

Hot dry summer, warm winter
Alice Springs, NT
AUS_NT_Alice.Springs.AP.943260_TMYx.2007-2021
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m

Climate type:
Example city:
Weather file name:
Annual heating demand:
Annual cooling demand:
Total thermal demand:

Hot dry summer, cool winter
Kalgoorlie, WA
AUS_WA_Kalgoorlie.AP.946370_TMYx.2007-2021
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m

NCC Climate zone 5 VURB
Climate Zone 5
NCC Climate zone 6 VURB
Climate Zone 6
NCC Climate zone 5 VURB thermal modelling

Climate type:
Example city:
Weather file name:
Annual heating demand:
Annual cooling demand:
Total thermal demand:

Warm temperate
Sydney, NSW
AUS_NSW_Sydney.Intl.AP.947670_TMYx.2007-2021
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m

Climate type:
Example city:
Weather file name:
Annual heating demand:
Annual cooling demand:
Total thermal demand:

Mild temperate
Melbourne, VIC
AUS_VIC_Melbourne.Olympic.Park_TMYx.2007-2021
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m
See below for Ceiling height of 2.4m to 3.5m

NCC Climate zone 7 VURB
Climate Zone 7
NCC Climate zone 8 VURB
Climate Zone 8
glazing calculator, performance solution, alternative solution, daylight modelling, cfd modelling, esd, bess, storm, sda report, smp report, energy compliance, energy efficiency, green star, jv3, nathers, star rating, vurb, nabers, gbca, ncc 2022, BCA facade calculator, climate zone 7
NCC Climate zone 8 VURB thermal modelling

Climate type:
Example city:
Weather file name:
Annual heating demand:
Annual cooling demand:
Total thermal demand:

Cool temperate
Hobart, TAS
AUS_TAS_Hobart.Ellerslie.Road_TMYx.2007-2021
See below for Ceiling height of 2.4m to 3.5m
Not significant – not required by the NCC
See below for Ceiling height of 2.4m to 3.5m

Climate type:
Example city:
Weather file name:
Annual heating demand:
Annual cooling demand:
Total thermal demand:

Alpine
Thredbo, NSW
AUS_NSW_Thredbo.Village_TMYx.2007-2021
See below for Ceiling height of 2.4m to 3.5m
Not significant – not required by the NCC
See below for Ceiling height of 2.4m to 3.5m

Conclusion

Comparing the results for each climate zone and between different climate zones, it could be concluded that:

ceiling height impact thermal energy modelling energy demand VURB JV3 Green Star DTS NatHERS
Table containing the results of ceiling height impact on energy use

  • In hot climate zones, the impact of ceiling height on thermal energy demand is not significant. For climate zone 1, changing the ceiling height from 2.4m to 3.5m increased the thermal energy demand by not more than 5% for the Reference Building. As a rule of thumb, for climate zone 1, the ratio of increase in room volume to the increase in energy demand is 9:1 (e.g. with a 9% increase in room volume, a 1% increase in thermal energy demand is expected).

  • For climate zone 2, the impact is not significant and could be neglected.

  • For climate zones 3,4 and 5, ceiling height variation increases the Reference Building’s thermal energy demand by no more than 15%. As a rule of thumb, for climate zones 3,4 and 5, the ratio of increase in room volume to the increase in energy demand is 3:1 (e.g. with a 3% increase in room volume, a 1% increase in thermal energy demand is expected).

  • For climate zone 6, ceiling height variation increases the Reference Building’s thermal energy demand by 20%. As a rule of thumb, for climate zones 6, the ratio of increase in room volume to the increase in energy demand is 2.5:1 (e.g. with a 2.5% increase in room volume, a 1% increase in thermal energy demand is expected).

  • For climate zone 7, ceiling height variation increases the Reference Building’s thermal energy demand by 30%. As a rule of thumb, for climate zones 6, the ratio of increase in room volume to the increase in energy demand is 1.5:1 (e.g. with a 1.5% increase in room volume, a 1% increase in thermal energy demand is expected).

  • For climate zone 8, ceiling height variation increases the Reference Building’s thermal energy demand by 45%. As a rule of thumb, for climate zones 6, the ratio of increase in room volume to the increase in energy demand is 1:1 (e.g. with a 1% increase in room volume, a 1% increase in thermal energy demand is expected).

  • Generally, the colder the climate gets, the more severe the impact of ceiling height on the thermal energy demand. For climate zone 6, 7 and 8, it is wise to keep the average ceiling height around 2.4m (standard ceiling height) as much as possible.