1. Impact of Architectural Form on the Potential Energy Performance of MURBs
(Multi-unit Residential Buildings)
Woytek Kujawski, M.Arch, MRAIC, LEED AP
Principal, Integrative Solutions Group Inc.,

2. How important is building form to the energy performance?
Combined impact of design parameters such as shapes, fenestration and shading strategies on the energy use of buildings
Designer’s dilemma: Geometry OR Envelope
Are there patterns to aid designers?

3. Importance of the early decisions
Decisions at the concept design stages of a project affecting building’s geometry, orientation, and glazing levels can have a significant impact on its lifetime energy performance.
This study / guidance can help designers to contribute toward good and sustainable solutions.

4. What can we say about IEQ or simply overheating?
Look at the curtains on most windows
How can we check what is going on?
Burnaby, BC
source: W.Kujawski

5. Plus new MURBs
What do we know about them?

6. What was studied? *
The relative impact the of different residential building forms and features on heating and cooling demands by conducting several thousand modeling simulations and analyzing trends.
The base:
3 building heights - 3, 5, 10 storey
5 floor plates - bar, square, L, H, U
4 orientations – N, E, S, W
Also the enclosure performance
3 wall assemblies, 6 window types and 3 window to wall ratios - 30%, 55%, 90%
3 balcony configurations:
no balcony, cantilevered and thermally broken balcony
* Study initiated by CMHC and delivered by former
Enermodal Engineering - MMM Group in 2013, today WSP Group

7. Gross Floor Plate Area (m²)
Suite layouts, numbers and areas
Floor plates with realistic suite layouts
Summary of Number of Suites and Gross Area for Floor Plate Used in Study
Floor Plate Geometry
Suites / floor
Gross Floor Plate Area (m²)
Square 12
1,003
Bar 22
1,586
'L' 20
1,459
'U' 34
2,525
'H' 52
3,934
(Note: heating and cooling loads were normalized by area, thus could be compared between all floor plates)
Courtesy of MMM Group/CMHC

8. Shapes and Orientation
Courtesy of MMM Group/CMHC

9. Brick Façade with cavity
Wall Constructions – Effective Values
Insulated spandrel U
Brick Façade with cavity
wall, insulated steel stud
cavity
1/2 U
Brick façade with cavity wall. Insulated stud cavity and exterior insulation between façade and interior wall
1/3 U
Resistance Conductivity
RSI-Value = 1 / U-factor
R-Value (IP units) ≈ 5.67 x R-value (SI units)
Courtesy of MMM Group/CMHC

10. Glazing Constructions – just for quick info
All glazings use argon gas
fills in aluminum frames with
9 mm thermal breaks.
Newly available double glazed window systems with a second low-e coating located on surface #4 (the interior exposed surface) offer a low cost option to improve the U-value without the high cost of triple glazed windows;
offering performance between traditional higher performance doubles, and super performance triple glazed windows.
Second low-e
coating
Fig. courtesy of MMM Group/CMHC

11. Glazing Constructions
Courtesy of MMM Group/CMHC

12. Metrics used to evaluate results
Heating and cooling energy “load” (intensity) - annual heating and cooling energy that should be provided by HVAC systems, therefore not including:
Boiler efficiency, Chiller efficiency, Distribution (pumps/fans), Internal (lights/appliances) gains
Should not be confused with peak or design day loads which are instantaneous values used to size space conditioning systems, or annual energy consumption which includes conversion efficiencies.
Allows comparisons between parameters that affect the building size (e.g. number of floors when normalized by building area (energy load / area)
Limitation:
Internal loads (i.e. lights, people, equipment, etc.) were not considered as part of this study.
Courtesy of MMM Group/CMHC

13. Metrics used to evaluate results
Context for kWh/m² consumption metric:
Space heating annual energy consumption (kWh/m²) is typically between 30% and 50% of the total energy consumption of a given MURB
Space cooling annual energy consumption (kWh/m²) is typically 2-5% of the annual energy consumption
Total annual energy consumption use intensity for MURBs ranges between kWh/m² and for high performance MURBs between 200 and 300 kWh/m².
Passive House MURBs can achieve less than 120 kWh/m²/yr
(not to be confused with PH heating load requirements of 15kWh/m2/yr).
Courtesy of MMM Group/CMHC

14. Impact of Balcony Configuration on Loads at Various WWRs
No major impact on heating loads
Shading effect of balcony in comparison to “no balcony”
Courtesy of MMM Group/CMHC

15. Space Heating Load Intensity – Floor plate and Orientation
No major impact on heating loads
-between 31,000 and 33,500 Wh/m2
The lowest
HEATING LOAD
COOLING LOAD 0°
90°
180°
270°
Wh/m2
Square
32,235
28,445
Bar
32,534
32,545
26,467
31,294
'L'
33,556
33,431
33,418
33,591
28,512
28,043
28,136
28,597
'U'
31,976
31,681
31,771
31,745
26,288
24,645
25,720
24,728
'H'
30,990
30,776
24,851
22,044
Courtesy of MMM Group/CMHC

16. Space Cooling Load Intensity – Floor plate and Orientation
despite the ‘H’ having a larger glazed area on all faces, the load is significantly lower than the Bar with the long axis oriented in the same direction
Minimal loads due to quick shading
during a day
No self-shading
Impact of self-shading in ‘H’ and ‘U’ as the East, South and West facing glazing located in the courtyards become partially or fully shaded when they would otherwise be left unshaded.
Fig. courtesy of MMM Group/CMHC

17. Space Heating Load Intensity – Number of Floors
the heat loss through the roof and bottom slab elements remains the same resulting in the decrease in the normalized annual heating load for buildings with more floors.
Fig. courtesy of MMM Group/CMHC

18. Overall envelope (window and wall)
system R-value (resistance) is strongly affected by WWR
Courtesy of MMM Group/CMHC

19. Heating Load Intensity vs. Window to Wall Ratio and Wall Performance
high WWR on lower U wall constructions vs. High U wall constructions
The bigger WWR, the smaller impact of quality wall construction; HOWEVER,
Wall with U-value of 1.2 (the effective performance of spandrel panels and IGU 2) can reduce its annual heating load with higher amounts of glazing due to the solar gains needed to offset the heat loss in envelope.
Fig. courtesy of MMM Group/CMHC

20. Putting it All Together – Heating and Cooling Energy Consumption in Bar shape
Courtesy of MMM Group/CMHC

21. Building Form Conclusions
Heating Loads
Orientation and floor plate have only minor effect
Number of stories (surrogate for envelope to floor ratio) has a larger effect, reducing the heating load intensity
Cooling Loads
Self-shading massing reduces cooling loads, while having only minor effect on heating
Number of stories increase the cooling load intensity

22. Building Form Conclusions - surprise
There were no preferred combinations of architectural form (floor plate, orientation and height) for any of the envelope parameters.
The impacts on the heating and cooling loads from the envelope parameters were relatively independent of the geometry.
higher buildings have reduced annual heating load intensity in heating season, and increased annual cooling load intensity in cooling season.
The best performing envelopes with respect to the heating load used low WWR (30%), well insulated walls and triple glazed windows with high solar heat gain low-e glazing;
the insulation level in the wall has a very small impact on the cooling load when compared to the heating load.
However, for summer cooling loads, low SHGC could be used sacrificing winter solar heat gains – a designer’s choice

23. Relative Impact of Architectural Features on Heating Loads
Envelope design is a sum of its parts
Envelope details affect loads independently of geometry
Courtesy of MMM Group/CMHC

24. Relative Impact of Architectural Features on Cooling Loads
Envelope performance is key. When the envelope is poor, massing and orientation can improve energy performance.
Good envelope performance allows freedom in massing/orientation
Courtesy of MMM Group/CMHC

25. Case Study –British Columbia, IDP charrette
Building Envelope – Initial and Corrected Ideas in envelope
High rise tower 14 floors
70% of the exterior wall area was designed in glazing
 The effective insulation value for exterior walls when taking into account insulated walls, glazing, eyebrows and balconies was RSI (R3)
- WWR was changed from 70% to 40%, windows changed to fiberglass
Bottom line: simulated energy savings achieved hundreds of $000s.
Courtesy of Chris Mattock

26. Canadian Reminder - The Arviat House Form Conclusions
Courtesy of Bill Semple

27. THANK YOU! These were directions for the effective design of MURBs…
What now?
These were directions
for the effective design of MURBs…
THANK YOU!
Lori Greig