Airtightness – is it all just a load of hot air??

No one likes a leaky building! You may not have thought about it before but I guarantee you have felt the discomfort of being in a draughty room. Much of sustainable building design relies of appropriate building materials and the orientation of windows and openings, these are the obvious aspects that are considered towards energy efficient buildings. However, if the building is not adequately airtight, any effort you might have made for insulation and orientation will be seriously compromised. Think about it – the idea is to keep heating or cooling INSIDE but if the nice warm/cool air is simply escaping out through poorly sealed building envelope, any insulation is rendered mostly useless. So to answer the question in the title – It is all about hot (or cool) air to achieve optimum thermal comfort at minimum cost.

Typical heat-loss pathways

The diagram above shows the common spots that contribute to poor airtightness…Junctions – roofs to walls, walls to floors; and openings – doors and windows and wall penetrations for services.

Regulations and guidelines vary on the level of airtightness required. From the best (Passivhaus) at 0.6 air changes per hour (ach) at 50Pa to British building regs at 10 air changes per hour.

Maximum air permeability	(m3/(h.m2) at 50Pa*
UK Building regulations – poorest acceptable standard	10
Building regulations indicative Part L 2010 target	7
Netherlands	6
Germany	1.8 – 3.8
Energy Saving Trust best practice	3
Super E® (Canada)	1.5
PassivHaus Standard	0.6
* Some values are actually air changes per hour @ 50Pa.

Buildings have to be constructed VERY well to achieve the passivhaus requirement of 0.6 and generally require the use of special membranes and taping to minimise air leakage. Airtightness tests are conducted during construction to check where levels are at and if more work needs to be done to achieve the desired levels (see image below)

Airtightness test carried out during construction

Where a building has less than 4 ach @ 50Pa, artificial ventilation will be required or the air quality will become unhealthy. (See previous blog post on this). Great for heat retention but bad for oxygen levels! The best systems in use are the Mechanical Ventilation Heat Recovery (MVHR) which uses heat from stale air being extracted, to warm incoming fresh air. You might be thinking, whats the point of making a building so airtight if you need energy to regulate air quality. But the energy used to run MVHR is minimal and costs about 50 pence per week and when you compare this to the reduced heating or cooling demand, there is no contest.

So, what kind of design decisions are required to achieve exemplar airtightness?

During my studies, SIGA did a workshop with us to educate us about their many products and how these should be used…

SIGA workshop at Oxford Brookes University

Membranes line out the entire inside of the building and these are fixed in place with tape and double sided sticky strips. Nails or staples should never be used as the piercings would compromise the integrity of the membrane.

All openings and penetrations are taped up:

SIGA product diagram showing where the products are used on a typical house envelope

There are typically two layers of BARRIER MEMBRANES in a good roof and wall design:

1. (RED LINE) the VAPOUR BARRIER (Airtightness layer) stops warm, moist internal air from getting into through the insulation and causing mould growth.
2. (BLUE LINE) the BREATHER  MEMBRANE (Weather-tight layer) allows moisture OUT but stops weather driven air and moisture INTO the building.

It is important to note that there is a difference between AIRTIGHTNESS and AIR INFILTRATION – the former refers to gaps in the building envelope which allow valuable warm or cool air to escape. Infiltration, however, is affected by wind loads / occupant behavior / natural ventilation strategies.

Energy Savings Trust has produced a document with some good case study information regarding this subject.

Find membranes and tapes at SIGA or INTELLO.

Next post I will look at the problems associated with Airtight buildings, namely poor air quality and mould and moisture issues, and how these can be avoided.

 

Earthday 2014

Today is EARTH DAY and there are many great environmentally friendly projects being promoted all over the world to mark this.

I particularly like this website and the content exploring FUTURE CITIES. We do indeed stand at a cross road, on the one hand – we continue to consume at an unsustainable rate and global warming sees our beautiful earth change for the worse – putting everything and everyone under great stress to survive. OR we prioritize development that is low-carbon and environmentally friendly: using materials and energy from renewable resources and limiting our excessive lifestyles to ensure that we waste less and re-use / recycle as much as possible.

For more on SUSTAINABLE FUTURE CITIES, click here.

 

 

Recycled building materials _ Car tyres

I found myself watching the Pixar animation WALL-E this afternoon and it is a sobering reminder of the possibility of an earth over-run by rubbish. One scene in particular shows mountains of old tyres and it got me thinking about how these are being used as building materials.

In the EU, tyres are prohibited from being thrown away and are one of the few materials that must be 100% recycled. Over 48 million tyres are discarded in the UK annually. There are a number of uses for old tyres – as discussed in this article from the Guardian in 2006  titled: ‘Tread Carefully: recycling tyres’ The following excerpt discusses the use as a building material:

Almost any brick wall could potentially be a tyre wall, says Mischa Hewitt, project manager at Earthship Brighton. The self-contained Earthship Brighton building, for example, contains 900 old tyres, weighing around nine tons. The tyres have to be filled with earth. “You shovel the soil in and tamp it down,” explains Mischa Hewitt. Using local earth is particularly eco-friendly, he points out, as there is no transport involved. “Earthships, for example, are often built into the sides of hills, so there’s a supply of soil there. Building is lower-impact if you aren’t moving stuff around.” Tyre walls will biodegrade in sunlight, but if they are rendered, they will last.

Earthship Brighton (Source: http://www.towntalk.co.uk)

The Earthship Brighton Building (above) is a Low Carbon project that uses various sustainable building methods to showcase how these work and educate people on their successes. Earthship buildings are nestled into the ground and require a solid rear wall construction to retain the earth. (More of the concept of Earthship buildings here.)

Example of tyre wall construction for an ‘earthship building’.

The process is quite simple – tyres are set in place, filled with earth which is then pounded with a sledgehammer to compact the soil and inflate the tyre. Once all the courses are in place, the tyre wall is rendered with adobe cement. This type of wall provides great thermal mass.

There are other examples of recycled tyre use in construction. Eurosheild have developped roof shingles that use 75% recycled material and estimate that a shingle roof on an average house would require 600 – 1000 tyres. An added benefit is that the tiles won’t warp or crack.

Durable and attractive roof shingles that consist of recycled tyres

The Daily Mail, published an article last year suggesting that the UK will soon use shredded tyre waste in the construction of roads. The tyre content will have a positive impact on noise pollution as road noise could be reduced by as much as 25%.  There are many countries that are already using ‘rubber roads’ successfully.

But back to buildings… there are plenty of examples of tyres that have been cut up and used as cladding like the following building at the Eden Project which uses flattened tyres as the roof…

Shelter at Eden project shortlisted for Architecture Journal award

You can read more about buildings that utilise recycled tyres among other materials, such as bottles and cans, at Earthship.com

Examples of earthship buildings from earthship.com

 

Pop-up House by Multipod Studio

Multipod Studio in France, have designed a prefabricated housing system that is quick to assemble, is completely recyclable and uses environmentally friendly materials.

The house totals 150m2 in floor area.

As visible in the time-lapse image above, the base floor raft is constructed of composite timber beams which use less timber than conventional raw plank timber framed systems.

The system uses insulation building blocks (EPS – expanded polystyrene) with thin timber framework, all fixed together with timber screws. Thermal bridging is minimized and the building envelope has a U-value of only 0.11 W/m2.k – and thus satisfies the Passivhaus requirement of max 0.15 W/m2.k.

WHAT DOES IT COST?

HOW IS THE BUILDING RECYCLABLE?

I think the overall look of the system is very appealing. Contemporary clean lines and the timber cladding softens the exterior. The charcoal colour of the insulation panels looks great with the timber and tends to blend well with natural surroundings.

The interiors are stylish and warm with timber floor and ceiling boards. Multipod also design great lights and furniture pieces, some of which are displayed in the image below.

Multipod studio have also developed an OFFICE POD.

Travel special: Amsterdam

Amsterdam is definitely on of my favorite cities. I decided this when we visited just this past weekend.

Amsterdam (Photo: Nathan Palmer)

As a city there is so much about it that makes it a wonderfully sustainable and efficient place to live. I refer mainly to the old city, which is where we stayed and spent most of our time but the more modern suburbs suggest that the dutch have continued to be world leaders in designing and developing low-carbon cities.

DENSITY & SCALE

The density and scale of the buildings ensures that space is maximized but one never feels overwhelmed. Typically 4 to 6 stories high, with retail on ground floor, the scale feels very comfortable. This is certainly assisted by the space between buildings – the narrow streets flanking picturesque canals – which dilute the impact of dense neighborhood living.

Typical city scale (Photo: Nathan Palmer)

The activity that ground level retail provides, results in a buzz and colour that makes every street unique and attractive.

TRANSPORT

The flat landscape and cycle friendly roads provide the ideal situation for commuting by bike. And there are thousands of them! According to wikipedia, ‘over 60% of trips are made by bike in the inner city and 38% of trips are made by bike overall in the greater city area’. It is quite something to cross the street as a pedestrian, and flinging ones head from left to right repeatedly becomes the standard road-crossing activity.

Bikes parked along the street (Photo: Nathan Palmer)

It is wonderful though, seeing so many happy cyclists, wind whipping through hair, kings of the road. That’s right – cars definitely take a back seat in this city. I would not be surprised to find out that there are as many bicycles as there are people in Amsterdam. It has caused some problem though as roads become filled with cyclists during peak hours and limited space for bike sparking caused frustration. The are now specific bike parking garages to deal with the vast numbers. I noticed this huge one outside the Central Train Station:

The tram system is well utilized and efficient which further discourages car usage and the associated pollution and carbon emissions. I do wonder why people have cars at all in this city.

PUBLIC SPACE

There are a number of bustling squares and peaceful parks in the city. Whether you are up for some street entertainment, or a quite stroll among leafy trees, you only have to amble a few blocks before you find what you are after. This access to pleasant public space has a profoundly positive impact on the health and well-being of occupants.

A small gripe would be that I found it annoying that general restaurant policy refused to offer tap water and one has to buy bottled water. This is both wasteful (use of bottles when the tap water is perfectly drinkable) and costly. I think that the city would do well to add more public drinking fountains around the streets as I only noticed one despite our extensive explorations.

BUILDINGS

Traditional narrow canal houses, with their narrow street frontage and deep footprint presents a planning challenge to be sure – especially with the placement of windows limited to front and back of the building. Although old and fairly poor insulation values for the typical building fabric, the terraced nature is very good for energy efficiency as the neighboring buildings act as insulation to the majority of the external walls. Contemporary improvements would include double or triple-glazed windows and , floor, roof and wall cavity insulation.

Energy Neural house by Faro Architects suggests a modern interpretation of the canal house in the suburb of Uberg, Amsterdam.

ENERGY

Amsterdam has one of the most advanced waste incinerators in the world. The heat sequestered provides the ‘fuel’ for district heating. The city is dedicated to shifting energy supply to renewable sources. The following facts and figures are sourced from http://www.iamsterdam.com here.

• The waste-fired power plant has an electrical efficiency of 30%, 8% higher than the average waste-to-energy plant.
• The AEB – Amsterdam’s Waste and Energy Company (AEB, Afval Energie Bedrijf) can produce sustainable energy because 48% of the waste consists of biomass. Energy released from biomass qualifies for CO2 neutral certification.
• The AEB produces 300,000 gigajoules of district heating per year. A household connected to the district heating grid uses an average of 36 gigajoules per year. In the near future, 40,000 additional households will be connected to the district heating grid provided by the AEB.
• The AEB produces renewable electricity for 320,000 households.
• The AEB produces 1 million MWh of electricity per year. This is enough to cover the electricity needs of three quarters of the households in Amsterdam. It is also enough to power a 60 watt light bulb for almost 2 million years.
• The AEB processes over 1.4 million tonnes of waste per year, and is the largest single location waste processor in the world. 1.4 million tonnes of waste are equal to the total weight of 185,000 African elephants!
• In 2007, the AEB avoided CO2-emissions equal to 470 kt. Just by generating energy from waste.
• There are about 123,000 street lights with 138,000 fittings and 145,000 light bulbs in Amsterdam. Green energy, delivered by the Amsterdam Waste and Energy Company, is used for all streetlights

Another source of renewable energy… Windmills – historic symbols of the Netherlands industrial success – are now being used to generate electricity. The community can buy shares in the windmills which allow them to benefit from future profits. Read more here  (tip: use google translate)

For more interesting facts and figure about Amsterdam, visit http://www.iamsterdam.com/en-GB/experience/about-amsterdam/facts-and-figures

Costs to achieve zero carbon buildings are falling – Zero Carbon Hub Report

One of the biggest hindrances to the construction of sustainable buildings is the extra cost incurred to achieve the improved performance. Despite the savings that one can experience during the life of the building as a result of lower energy bills, the build costs upfront are a deterrent. As building regulations improve to demand high quality, high performing, low carbon buildings, the gap between national regulations and exemplar standards (eg. Passivhaus and Code for Sustainable home level 6) is diminishing.

The LIGHTHOUSE by Sheppard Robson Architects was the first UK building to achieve zero carbon (Code for Sustainable Homes level 6) status.

ZERO CARBON HUB has recently released a report on the costs associated with Low Carbon buildings: Cost Analysis: Meeting the Zero Carbon Standard, Feb 2014. (All images and tables are extracted from the report.)

The findings are very encouraging. The results show that the additional costs associated with reaching Low Carbon buildings has roughly halved since the previous report in 2011. Additionally costs are expected to continue to fall between 2014 and 2020.

At Today’s prices, the additional cost to build a semi-detached dwelling to zero carbon standard is in the region of £5000.

The elements that contribute to the zero carbon standard are as follows:

1. Fabric Energy efficiency should contribute the greatest componant and refers to the insulating properties of the building envelope. High performance windows and openings, well insulated roofs, walls, and floors
2. Low / zero carbon technologies are used to reduce energy demand from non-renewable fuel sources (gas & coal-powered electricity). These typically include solar PV (electricity), wind turbines, Solar hot water systems, and Heat pumps (ground / air-source) etc.
3.  ‘Allowable solutions’ refer to a government scheme to offset additional carbon use by investing in projects that aim to improve carbon reduction in various industries.

Key findings of the REPORT:

• Continuing drop in costs associated with reach low carbon standard for dwellings. Particular reductions in cost estimates for Solar PV, air-tightness and thermal bridging components.
• Reasonable additional costs are found to be:
  • Detached dwelling = £6700 – £7500
  • Semi-detached = £3700 – £4700
  • Apartments (low-rise) = £2200 – £2400
• Costs will continue to fall from 2014 to 2020 – resulting in additional costs for detached dwellings = £5700 – £6300; semi-detached = £2900 – £3600; apartments = £1900 – £2000
• These costs assume the lowest capital costs associated with zero carbon standard – this requires the use of Solar PV.
• The cost of solar PV is expected to fall at a greater rate than the cost of improved building fabric solutions such that the use of PV will achieve a zero carbon solution at lower cost that a Passivhaus solution (to use an example of Advanced energy efficiency scenarios).
  • Cost of PV has dropped from around £3800 / kWp in 2010 to £1500 / kWp today.
• Table below shows a summary of cost breakdown for the 4 different housing types.

 Energy targets associated with different dwelling types:

 

This report is most encouraging as we strive to boost the number of new buildings (and retrofitted buildings) that are zero carbon. Thanks to the Zero Carbon Hub for this report and for making the costs associated with green buildings easier to interpret and therefore entertain.

Image courtesy of Zero Carbon Hub: Cost Analysis Report 2014

Project 24, Bangor, Northern Ireland

I have recently returned from a holiday to Belfast, Northern Ireland and I love the opportunity that travelling affords to discover great projects. We came across this brilliant project which started in April 2013.

PROJECT 24 : What was a fairly derelict plot of land in the town centre has been cleverly revitalised. Brightly coloured Shipping containers are dotted around and provide studio’s for artists. Six pods each containing 2 artist studios. Following an application process, artists take residence in the pods and both create and sell their art for the duration of their tenancy.

Vibrant shared space

This ticks a number of sustainability boxes:

• Re-use of existing ‘dead’ space and adds value to the local community.
• Easily accessible by public transport and high foot traffic due to the central location.
• Art and culture is encouraged as artists and the wider community interact.
• Community garden encourages locals to grow food bearing plants which enhances biodiversity, is good for health and education.
• The pods are constructed from dis-used shipping containers which are particularly relevant for the area as Belfast has current and historic links with the shipping industry – most notably, the birthplace of the Titanic.

Rawlemon’s spherical solar energy collector

Rawlemon have designed a glass globe that tracks the sun (and moon) and concentrates the light up to 10000 times. The company claims that it is 35% more efficient than photovoltaic panels.

Rawlemon devices harness diffuse light, so they can work at night as well as during the day (Gizmag)

The sun’s energy is concentrated towards a small surface area of photovoltaic cells

See video clip here.

Fabric First! -the Passivhaus standard

When it comes to sustainable building design, a key phrase is FABRIC FIRST. In essence this means that the primary objective when designing a green building should be exemplar wall, window / door openings, roof, floor composition to ensure that the transfer of heat between inside and outside is minimized. The INSULATION value of the building envelope.

Where this is achieved, the energy required to maintain thermal comfort indoors will be dramatically reduced.  Hand-in-hand with the insulation levels, is the AIR TIGHTNESS of the building. For it would be of little value if the building had great insulation values but high infiltration such that the hot / cool air merely escaped through gaps in the enclosure.

The PASSIVHAUS standard, developed in Germany in 1990s,  is a specific energy performance standard that delivers very high levels of energy efficiency and thermal comfort. With stringent requirements for the U-values of the building fabric and air tightness, Passivhaus buildings have little or no heating / cooling demand. It is widely recognized as the global leader in the fabric first approach to low energy buildings.

Benefits of a Passivhaus building:

• ultra low fuel bills and much less exposure to energy price rises
• unrivalled indoor comfort – no drafts or cold spots in winter
• cooler indoor temperatures in summer
• improved indoor air quality bringing many potential health benefits
• quieter indoor space when the triple glazed windows are closed
• better use of your available floor space – no radiators
• lower maintenance costs – less technology to go wrong
• greater building fabric durability
• huge variety of styles, layouts and materials that can be employed

(Source: http://www.passivhaushomes.co.uk/why.html) 

GUIDELINES

Energy performance targets and air changes per hour
Specific Heating Demand	≤ 15 kWh/m2. yr
Specific Cooling Demand	≤ 15 kWh/m2. yr
Specific Primary Energy Demand	≤ 120 kWh/m2. Yr
Design Component	Limiting value
Walls, Roof, Floor (U-values)	≤0.15 (W/m2K)
Installed glazing	≤0.85 (W/m2K)
Doors	≤0.8 (W/m2K)
Infiltration (ach-1)	≤0.6 @ n50
Thermal bridging (linear ψ value)	≤0.01 (W/mK)
MVHR coefficient (η HR)	≥0.75
Ventilation electric limit	0.45 Wh/m3
Appliances	High efficiency recommended
Lighting	High efficiency recommended
On site renewables	No requirement but SHW typical

© Passivhaus Institut WSchVO = German Heat Protection Regulation SBN = Swedish Construction Standard

VENTILATION REQUIREMENT

You will notice for the graph above that there is an energy requirement for ventilation. This is owing to the low infiltration achieved, thus fresh air must be circulated through the building. This a generally achieved by means of an MVHR (Mechanical Ventilation with Heat Recovery).

This system takes heat from outgoing stale air to warm incoming cool air. Air is EXTRACTED from Bathrooms and Kitchens and SUPPLIED to living areas such as bedrooms and lounge. (The heating of the air can be switched off in summer to avoid unwanted heat gains.)

RESOURCES

There are many websites and books that help to understand and apply the Passivhaus principles. If the certification is what you are after, you need to use the Passivhaus Planning Package which will ensure that you have met the requirements. (Buy Here)

Passipedia is a great online resource with details, links and discussion forums.

CASE STUDIES

Crossway Passivhaus, UK (Hawkes Architecture)

Camden Passivhaus, London (Bere Architects)

Bessancourt, France (Karawitz Architects)

Oakmeadow Primary School, Wolverhampton (Architype)

Useful PASSIVHAUS summary document here.

How to design fitter cities? City Health Check – a Report by RIBA

This report was released by RIBA (Royal Institute of British Architects)

‘Our analysis finds a clear correlation between the least healthy local authority areas in cities, and the amount of housing and green space in those areas.’

The design and space planning of cities can and does have a huge impact of the health and well-being of those who occupy these spaces. The contents of the report include case studies and design analysis that is most useful for planning.

Two clear conclusions are formulated:

1. There is a clear link between land use and public health in cities

2.  People say it is the QUALITY not quantity of streets and parks that will encourage them to walk more.