a2m.be
2019.04
futureproof design
cost
Certain people claim that building to the passive standard costs 2.4, 10 or even 20% more than conventional buildings. They are right! Because the passive standard involves thicker insulation, better airtightness and a ventilation system and all this obviously costs more. Nevertheless, an increasing number of passive buildings are achieving similar, or even lower, overall costs compared to benchmark prices, leading some people to declare that building to the passive standard is cheaper than building conventionally. And they are also right! 2
However, if everybody is right, where does the truth lie?
cost efficient solutions for a resilient future
cost efficient solutions for a resilient future 3
A large number of economic methodologies are based on partial perspectives, reducing for instance the passive standard to “all you need is a bit more insulation!”. As shown by more than 900,000 m² of passive buildings completed or being built in Brussels by 2015, reality is shows that things are not that simple. Day-to-day practical experience reveals that building to the passive standard involves a lot more than just a few additional centimetres of insulation. There are a lot of factors influencing the final cost that need to be taken into account. In the course of our
design, each project is constantly reviewed to make sure it stays within a budget acceptable to all concerned. While there are no hard-and-fast rules regarding the cost of passive construction, there are certain factors with a positive influence – meaning that a passive building can end up with a price tag similar to that of a conventional building – and ones with the opposite effect.
cost efficient solutions for a resilient future
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cost efficient solutions for a resilient future
Les Balcons Š A2M | photo Š Stijn Bollaert
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cost efficient solutions for a resilient future
how does A2M achieve hyper efficient buildings at a lower cost?
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In 2005, A2M was surprised to find that, in response to a call for tender for its first passive building project, 7 of the 9 tenders were lower than the estimated cost. This project ended up being completed at a cost equivalent to 90% of the planned budget by the contractor which had put in the cheapest bid. After acceptance and the final settlement of accounts, the project ended with a price tag 5% below what was usual for a comparable project. In 2012, A2M with a general contractor put in a bid for a public Design & Build call for tender for a 13550 m2 complex consisting of a school for 450 children, 51 apartments and offices issued by the City (Régie Foncière de la Ville de Bruxelles). Bids ranged from 12,8 to 19,6M€ (taxes ex.). Of the 17 bids received, 4 proposed a passive building, while the rest were a low-energy building (in dark green on the graph).
Though the least expensive bid (1057€/m2*) was for a low-energy building, the next two were for a passive building (1085€/m2). Among them, our projected cost was far below the average (average cost 1340€/m2) and much less than the most expensive bid (1605€/m2) – for a low-energy building. The project was naturally awarded to the most competitively priced and efficient project. In this case as with most of the best value/ efficiency projects, the key was that all A2M staff is trained on energy demand calculations, and thermal engineers are integrated as part of the team. There are very few architect offices that are able to talk the “energy” language. The other parameters are detailed on the following pages.
* construction cost tax excluded
cost efficient solutions for a resilient future
passive projects low energy projects
2000 1800 1600 1400 1200 1000 800 600 400 0
price â‚Ź/m2 exclusive of VAT of offers submitted in design & build
energy cost saving for A2M’s projects since 2007
$
4,5m 4m
42%
3,5m
facades
3m The Particular Land Use Plan, and the project selected beside
2,5m 1,5m 1m 500K 0
2007
cost
efficient solutions for a resilient future2014 2015 2016 2017 2018 2011 2012 2008 2009 2013
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8
cost efficient solutions for a resilient future
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cost efficient solutions for a resilient future
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cost efficient solutions for a resilient future
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cost efficient solutions for a resilient future
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cost efficient solutions for a resilient future
what are the determining factors? The key to achieving the best efficiency cost rate for any project is the design team. Our experience as architects shows that it’s an absolute requirement to understand what’s going on with the energy aspect when designing the envelope of a building. In the Passive House approach, comfort is not only achieved through mechanical systems, so the performance can’t be split from the envelope design. During the process, the key to cost control is that the architects are able to understand and discuss with the engineers, because most of the building efficiency will be determined by the envelope. Based on our experience, there are several other factors influencing costs: —— Project size: as in any market, economies of scale often play a determining role; —— Building typology: Refurbishment projects are always one-off projects, requiring a project-specific approach and specific systems, all of which push the price up (especially when heritage conservation aspects come into play); —— The structure of the building: (the cost of the structure, whether “heavy” or lightweight, is determined by the market. In Belgium, for example, the market for “masonry” constructions is much larger, and so more competitive, than for timber-framed constructions…
—— special features: when a building incorporates special features (overhangs, innovatory systems, etc.), it will be more expensive, regardless of whether it is a passive or conventional building. —— Finishings are also a key factor, and it is often possible to find finishings at a lower price. —— Compactness: where buildings are relatively compact, it is generally easier to achieve the required energy performance; this also makes it possible to reduce insulation thickness or even to revert to double glazing. —— The targeted energy performance: in the case of a building exceeding the passive standard, energy-saving technologies often represent a significant part of the budget. —— The project delivery system: Design & build delivery systems allow all players involved in a project to be brought together right from the design phase. This helps in finding comprehensive solutions encompassing all aspects of the project (architecture, functionality, cost, etc.). —— Last but not least, the proper use of software tools (PHPP, calculation of thermal bridges, etc.) often allows a project to be analysed from a thermal point of view, playing with different parameters to optimise their financial impacts.
cost efficient solutions for a resilient future
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comparing prices and materials
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With insulation, airtightness and ventilation being aspects that may be somewhat abstract for certain readers, it is a good idea to look at a few orders of magnitude regarding market prices in relation to the specific properties of these products. Starting with insulation, having an overview of overall heat losses can help find the best way of allocating insulation. An interesting proposition is to use thicker insulation where insulating costs less (i.e. the roof) and to reduce the energy performance of elements that are more expensive (e.g. window frames).
expensive to eliminate (insofar as they do not present a health risk), concentrating one’s efforts instead on ones with a greater impact (through investing in better facade insulation for instance). The tables above compare several types of insulation material, showing the average price for the same thickness or the same performance.
This also applies to thermal bridges, the impact of which must be calculated with great care. If the project has been designed with a certain leeway (+/- a few kWh/m² p.a.), it might be possible to ignore certain thermal bridges that are too difficult or too cost efficient solutions for a resilient future
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roof 10 5
PIR 50
comparing prices and materials – roof
A – price per m² at equal thickness (mm)
since 2007
ades
LAINE MIN. 50
CEL GLAS 50
EPS 50
XPS 50
B – price per m² at equal performance (0,12 W/m²K)
compar
Price per m² at equal performance (0,12 W/m²K)
Price per m² at equal thickness (mm)
2%
PU 50
P
€
€
€
50
500
50
45
450
45
40
400
40
35
350
35
30
300
30
25
250
25
20
200
20
15
150
15
10
100
10
5
50
5
PIR 50
PU 50
LAINE MIN. 50
CEL GLAS 50
EPS 50
XPS 50
PIR 220
PU 220
MIN. WOOL 320
CEL GLAS 360
EPS 320
XPS 260
EP
15 2016 2017 2018 Price per m² at equal performance (0,12 W/m²K)
Price p
€
€
500
100
450
90
400
80
350
15 70
300
60
250
50
200
40
150
30
es trough in/exfiltration 100
20
50
10
PIR 220
PU 220
MIN. WOOL 320
CEL GLAS 360
EPS 320
XPS 260
EP
floors 17% windows 17%
24%
24%
roofs
roofs
42%
42%
facades
facades
17%
17%
windows
windows
17%
17%
floors
floors
cost efficient solutions for a resilient future
facades 42% roofs 24%
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A comparison based on an equivalent performance is obviously a lot more interesting when choices have to be made during the design phase. Nevertheless, one needs to take all of the parameters into account: where thicker insulation has to be used to achieve the same performance, this can have other financial consequences: —— Roofs and floor slabs: to maintain compliance with internal dimensions, this extra thickness means that the walls will be higher. The additional metres of wall (parapet walls, etc.) thus need to be taken into account. —— Outside walls: total floorspace may be reduced as a result of using thicker insulation, meaning that the overall cost per surface will increase. In large projects, this can often have quite a significant financial impact.
—— Window frames: it would seem that a frame’s material (and not its energy performance) often determines the price. Again, it is interesting to take all factors into account: Uf, Ug, glazed surface, etc. For example, aluminium window frames with a lower Uf may end up with an overall result just as interesting as other types of frame with better insulating properties, as aluminium frame crosssections are generally thinner, allowing greater glazed surfaces and thus letting in more sun. Finding the optimal solution is obviously dependent on the specific features of each project.
cost efficient solutions for a resilient future
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wall 10 5
50
EPS 50
XPS 50
comparing prices and materials – wall
A – price per m² at equal thickness (mm)
m²K)
EPS 320
XPS 50
NEOPOR EPS + PU 50 50
PU 50
B – price per m² at equal performance (0,12 W/m²K)
Price per m² at equal thickness (mm)
Price per m² at equal performance (0,12 W/m²K)
€
€
50
100
45
90
40
80
35
70
30
60
25
50
20
40
15
30
10
20
5
10
ene 1.200.000 1.000.000 800.000 600.000 400.000
XPS 260
200.000
EPS 50
XPS 50
NEOPOR EPS + PU 50 50
PU 50
EPS 320
XPS 260
NEOPOR EPS 20 260 + PU180
PU 200
Price per m² at equal performance (0,12 W/m²K)
€ 100 90 80
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70 60 50 40 30 20 10
EPS 320
XPS 260
NEOPOR EPS 20 260 + PU180
PU 200
ors 17%
dows 17%
ades 42%
fs 24%
cost efficient solutions for a resilient future
inside
outside
airtightness continuity insulation continuity
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Airtightness: it is vital to define the right method or the right product in line with the way the building is built. In addition to the price of materials, the time it takes to install them and their ease of use are determining factors. Achieving airtightness through the use of dry-lining is probably the best known method in Belgium and the easiest to implement compared with other more demanding and newer methods involving membranes and adhesive tape. Proper site planning, the right implementation and blower door tests help minimise airtightness problems.
Understanding the priorities: dependent on their form and how they are implemented, junctions with a parapet wall can have a major or absolutely negligible effect, and it is important to determine the influence of such a junction on the building’s overall energy footprint before setting any priorities.
cost efficient solutions for a resilient future
three simple principles
isolation
étanchéité à l’air
The passive building standard does not contain any formal, material or aesthetic restrictions, making it very attractive and extremely flexible. Based mainly on calculations, it is for instance a lot less restrictive than certain current urban planning regulations. Though a large north-facing window would obviously have a negative impact on heating requirements, this can be compensated through the use of a material with better insulation properties, through thicker roof insulation or through a slightly more efficient energy recovery ventilation. The purpose is not to come up with readyto-use “recipes”, but instead to look at various points requiring attention and to provide construction strategies, with the overall aim of achieving the optimal balance between thermal, aesthetic and energysaving aspects and construction reality.
ventilation
As with any high-performance construction, the passive building standard requires particular attention to be paid to the building’s envelope, with the focus on three interrelated aspects: insulation, airtightness and ventilation. Finally, when designing a “low-tech” passive building, there should be no sacrificing of comfort in favour of technical systems. With a building’s level of comfort closely connected with its physical properties, proper coordination between the client, architect, design team and building company is of key importance for successful project completion.
cost efficient solutions for a resilient future
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case study: window frame
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Due to the change in the building materials used, a linear disruption occurs where the windows join with the walls. Even if seemingly not that harmful, such disruptions are to be found repeated throughout the building and can have an impact amounting to several kWh/m² p.a. on the overall energy footprint. The position of the frame in relation to the insulation also plays a determining role, as we can see in two extreme external insulation examples. The 12°C isotherm is in red. In the second example, it can be seen to be getting dangerously close to the inside surface, with the wall approaching 13°C. This situation, as well as being uncomfortable for an occupant, also brings with it the risk of condensation. From a strictly thermal point of view, the frame’s optimal position is when it is flush with the insulation. This is quite simple to achieve when for example the insulation is integrated in a timber structure, but more
complex when the window is part of a brickbuilt wall, where this would lead to the frame jutting out into the outside insulation. This complicates the fitting of windows (corner irons, cuts, junctions). From a practical and cost-efficient point of view, a good solution is to have the fixed part of the frame itself covered by the external insulation, thereby reducing the negative impact of the thermal bridge without causing any undue installation work. From a thermal point of view, though this method is not optimal, it does not require lots of cuts in the insulation and allows the insulation to be fixed to a smooth surface, thereby speeding up installation and keeping costs down. Last but not least, the result is better in terms of continuous insulation.
Where a brick-built wall is involved, installing a layer of insulating blocks under the sill.
cost efficient solutions for a resilient future
optimized design A – the frame is suspended into the exterior insulation (EPS)
1
2
4
5 1 – plaster 2 – croncrete block 3 – air tightness 4 – Neopor© graphite-impregnated EPS isolation 5 – STO© external coating
3
cost impact
€€€€€ thermal bridge impact Ѱ = -0,11 W/m.K
B – the frame stays within the bearing wall and is covered by the exterior insulation (EPS) 1
2
4
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5 1 – plaster 2 – reinforced concrete wall 3 – air tightness 4 – Neopor© graphite-impregnated EPS isolation 5 – STO© external coating
3
cost impact
€€
thermal bridge impact Ѱ = -0,12 W/m.K
cost efficient solutions for a resilient future
optimized design A – extension under frame with Perinsul insulating block
B – extension under frame with light aerated concrete block
2 3
1
2 5
4
cost impact
€€€€€
22
7
6
1
thermal bridge impact Ѱ = 0,032 W/m.K
5
4
6
cost impact
€€
thermal bridge impact Ѱ = 0,028 W/m.K
1 — plaster 2 — window sill on air tightness strip 3 — Perinsul insulating block 4 — concrete block 5 — Neopor© graphite-impregnated EPS isolator 6 — STO© external coating 7 — Xella© light aerated concrete block
cost efficient solutions for a resilient future
This type of junction represents a good compromise between the thermal footprint and ease of installation. Such solutions are often dependent on the quality of collaboration and the flexibility of the project's design and construction team.
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cost efficient solutions for a resilient future
cost efficiency and cost management
Construction costs can be disturbingly high. Since 1975, the average price of a house has risen more than 10 times, while the general price index has only increased 3.5 times. Between 2004 and 2013, the construction cost index has risen 33% in France and 25% in Belgium. 24
The sector has experienced a major hike in the costs of certain materials and energy, without speaking of land prices and the length of time required to process planning applications. On the other hand, the improvement in a building’s energy efficiency, health quality and acoustics are also factors contributing to this rise in costs. The whole concept of cost is in itself a very complex subject, with the “true” price not just involving the construction costs, but also the cost of operating a building over the years. Using this “total cost of ownership” (TCO) concept covering the building’s whole life cycle allows us to distinguish between pure expenditure items and those leading to savings (in particular energy-related ones) and usage benefits.
There is also debate on the economics of passive buildings. There are a number of completed projects showing that it is possible to construct passive buildings at a price above or below the conventional average. This is hardly surprising, as passive construction is an emerging practice. Yet this caution leads us to neglect a fundamental aspect: when current-day projects ignore the climate and energy agendas in their energy-related dimension – i.e. when they are unable to achieve a nearly-zero energy status (nZEB) - they will at some stage have to be either upgraded at considerable expense or demolished. Ongoing energy transition demands that such half-measures be avoided. In the absence of a general rule (each project has its own specific characteristics), this chapter provides a few thoughts on budget control.
cost efficient solutions for a resilient future
analysis exemples
thermal bridge analysis
life cycle assessment
daylight analysis
4 000 000 € 3 500 000 € 3 000 000 €
end of life cost maintenance cost
2 500 000 €
operation cost construction cost
2 000 000 € 1 500 000 € light facade 1
light faacde 2
light facade 3
light facade 4
massive facade 1
massive facade 2
massive facade 3
massive facade 4
Impact budgétaire sur durée de vie LCC (30 ans) Le calcul LCC a été testé sur 8 type de composition de façade. La solution retenue est une façade de type «massive»
25 parametric design
vapor control analysis
daylight factor
cost efficient solutions for a resilient future
life cycle cost
A2M case studies
compared to benchmark
Because some figures are more valuable than thousands of words, here are some selected works done by the office. We retained only finished or close to ending projects, so the prices mentioned are the actual final calculations. Prices are construction costs, fee and taxes not included. Surfaces are gross area, and half of underground if present. 26
For each project, we compared the actual price with the benchmark for correspondent work, location, scale.
cost efficient solutions for a resilient future
compared to benchmark
01
A2M case studies
embassy of Belgium & The Netherlands We won the competition (design and build) because the project was not only the cheapest, but also the most efficient! This is the first Passive House building of Africa, needing 70 % less air conditioning to achieve comfort compared to the competitors.
situation boulevard du 30 Juin, Kinshasa, RDC
€/m² 1213 €/m2 (competitors: 2500 €/m2)
project type new construction
performance passive | 15 kWh/m².yr (cooling needs)
building function offices for belgian embassy
annual saving energy cost 43 354 €/yr
construction cost (ex. VAT) 7 422 500 €
status delivered
client public | Belgian Foreign Affairs Ministry project scope 5769 m² extra passive building
project delivery method Design & Build (DB)
7 422 500
43 354
-45
€
€/yr
kWh/m².yr
construction cost savings
energy anual savings
efficiency improvement
cost efficient solutions for a resilient future
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02
A2M case studies
compared to benchmark
anvers-simons On the 17 entries for this competition, only 4 proposed to reach the Passive House standard. Our proposal was not only among the most efficient but was also the cheapest. The range went from 27M€ (and this with only low energy efficiency) to our offer (D&B) with the contractor of 13M€ only and with Passive house.
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situation rue Simonis + ch. d’Anvers + rue Frontispice, BE
€/m² 1094 €/m² ( 1300 €/m² Benchmark) performance passive <15 kWh/m².yr (heating needs)
project type construction + renovation building function 51 housing units, primary school and kindergarten, welcoming spaces construction cost (ex. VAT) 13 363 048 €
BATEX
annual saving energy cost 19 026 €/yr
client public | Régie Foncière de la Ville de Bruxelles project scope 13 369 m² extra passive building, Exemplary Building Award 2012
status delivered project delivery method Design & Build (DB)
2 510 602
19 026
-55
€
€/yr
kWh/m².yr
construction cost savings
energy cost savings
efficiency improvement
cost efficient solutions for a resilient future
compared to benchmark
03
A2M case studies
belle-vue The Bellevue Brewery is renovated into a 150 rooms hostel. After one year of 90% occupation, the management called, thinking that there was a problem with the meter, because the energy bill was so low! For around 600 persons a day, the energy cost is only 2950 € per month while it’s normally 10 times this cost in their similar hotel.
situation quai du Hainaut 33, Molenbeek-Saint-Jean, BE project type renovation building function 150-room hotel/ apartement block (14 units) construction cost (ex. VAT) 9 585 400 €
BATEX
€/m² 1100 €/m² ( 1450 €/m² Benchmark)
project delivery method private bid
performance low energy | 20 kWh/m².yr (heating needs)
client private | Nelson Canal sa project scope 8714 m²
annual saving energy cost 109 674 €/yr
extra renovation of the former Belle-Vue brewery into a low energy building, Batex 2009
status delivered
3 049 900
109 674
-116
€
€/yr
kWh/m²yr
construction cost savings
energy anual savings
efficiency improvement
cost efficient solutions for a resilient future
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we do architecture very modern architecture passivhouse standard only prepress for magazine & books believe in building physics thermal bridges, moisture & neutral lightening simulations work like hell
we don’t overcharge outsource building physics restrain our diverse activities understand chaos theory we will make you smile work for right cause value your projects increase your ambitions build a better world
we are not "bio" extremists close minded only architects aliens neither wise in the ways of kung fu we won’t let you down
Since it was founded, A2M has set itself the goal of making our world more liveable by championing quality contemporary architecture with high environmental value. Although all A2M’s projects achieve passive house performance (and for some also Net Zero Energy, Exemplary Building, or Breeam) most are priced at an equivalent to or even lower than the standard market. The A2M team is composed of architects, engineer architects and thermal engineers. All specifically trained in different aspects of sustainable development, passive design, natural light analysis as well as dynamic simulation. These skills gathered under one roof enable us to combine the economic with the exemplary dimensions in each of our projects.
a2m.be
— ©CO2 neutral certified company
permacity A2M
we share
we build
4 144
1 238 139
passive house dwellings 496 completed or in construction
m2 passive house [12 381 392 SF] 202 384 m² completed or in construction
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exemplary buildings awards
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1
MIPIM AWARD
20 + 14
office buildings
schools & kindergardens
permacity A2M
941 285
m2 zero energy [9 412 858 SF]
6
BREEAM / 52 876 m2 completed or in construction
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hotels
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Editor in charge: Sebastian Moreno-Vacca – A2M, chaussée de Boondael 6 (bte 13), 1050 Ixelles – BE
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