Household Moisture – Its in the Furnishings and Materials

Household moisture primarily resides in the building materials and furnishings in a house.  Think your big, damp mattress, for instance.
Damp materials in your house keep your relative humidity high.  And releasing humidity into the air means that moisture will eventually find its way inside your couch, or in other furnishings or building materials.
Here is a simple chart of the equilibrium relationship between moisture in the air (RH), and moisture in materials (MC), expressed as a percentage of the mass of the material.
This chart can be read as follows:  If you house averages 70% humidity, you can follow the 70% RH line and see that spruce wood (similar to pine), will have about 13% moisture content.  Given that your house will have thousands of kg of pine in it, this chart means there will be hundreds of kg of water in that material.  And the same with wallboard, insulation, soft furnishings, and your carpet.

For experimental purposes, or for learning with school kids, a simple hygrothermal (heat and moisture) model of a house can be built as so:

Read about our recent research with the Valley Community Workspace community group: (PDF)
Also see “The Wetting and Drying of Timber Framed Walls


Building Activity

How many houses are being built in New Zealand? And where?  This question and more can be answered using SHAC’s Building Activity app.


Damp Homes

Imagine, if you take a cold and damp house, and then wrap it in extra insulation and draughtproofing.  What do you get? A warm and damp house.  The extra insulation and draughtproofing reduce the air circulating in a house, which is a reduction of the ability for a house to dry itself.

How do we get a warm and dry house?  Capture the sun, add heating to the house, and add ventilation. This can be as simple as ensuring the windows of a house are open during the day, especially when it is sunny out.  Or you can add some sort of ventilation system that takes in outside air into the house.  Your heat pump does not do this – all a heat pump does is recirculate the damp air that is already inside your house.
On the whole, outside air is dryer than inside air, especially once it is heated to inside temperatures. This is why bringing outside air into the house helps to dry the house. There is some cost to heating outside air, but the benefit is a dryer, healthier house.  Also, if a ventilation system is used, this cost can be reduced if a heat recovery ventilation system is used. Of course using windows for ventilation is the cheapest option of all!

Psychrometric chart showing WHO recommended temperature and humidity (green+blue region), and room measurements for one week. Each point is average temperature and humidity for one hour. Different times of day are coloured differently.

Most of the moisture (>85%) in a house is in the furnishings and building materials in the house. Simply removing moist air once will not dry a house, as dampness will just evaporate from furnishings and building materials, and the air will quickly become damp again, within minutes. A damp house needs repeated flushing of the air within the house so that the furnishings and building materials within the house slowly begin to dry.
Read about our recent research with the Valley Community Workspace community group: (PDF)
Also see “The Wetting and Drying of Timber Framed Walls


Addressing the challenge of climate change together, activists and designers

… Climate activism has primarily manifested as “Blockadia.”  Why? Blocking and shutting down bad projects is easier to organize around than efficiency or carbon pricing. And maybe that’s fine. Maybe it isn’t the role of activists to imagine and bring about a new world. Maybe that’s for policymakers, designers, engineers, artists, and entrepreneurs.

Source: Architecture and Climate – what critics misunderstand about climate activism

2015 Challenge Finalists 2015_Challenge_Shortlist MicroArchitecture

Sunset Stripes [2015-30]

Our project consists of rammed earth walls, Douglas fir panelling and seating, a concrete floor, and steel roofing. There are two entrances, the main one opening onto the road, and a smaller secondary entrance at the rear of the shelter allowing access from the resort. The walls at the back overlap at the entrance to stop the cold southerly winds entering the shelter. There is vertical panelling on part of the front entrance to deflect the chilly North Westerly winds while allowing in the morning sun from the East. The main opening faces North allowing sun to stream in all day and views of Mt Hutt. The rammed earth walls combined with timber panels and seating give the shelter a warm and cosy feel. The roof drains to a single point at the rear, then trickles down a chain drain into a small wishing well. It seats approximately 16 people.
2015-30 Sunset Stripes A3PNG_Page_2-small 2015-30 Sunset Stripes A3PNG_Page_1-small

2015 Challenge Finalists 2015 Challenge Winners 2015_Challenge_Shortlist MicroArchitecture

Mountain View [2015-13]

Inspired by the beautiful mountain view of Mt. Hutt from the site, the Mountain View bus shelter allows people to enjoy the spectacular mountain scenery while waiting for the bus to arrive. The bus shelter also incorporates natural materials such as straw bale, local wood (Douglas fir), and green roofing to provide a sustainable and aesthetically pleasing shelter for both the tourists, and the local community of Methven.
Materials used are the following:
Strawbale plastered with lime for the south part of the bus shelter that functions as a load bearing wall, which withstands southwesterly prevailing winds.
Also a great natural and sustainable material that provide insulation
Untreated local (Douglas fir) wood used for the overall framing of the shelter.
Recycled glass are used for the visibility of the mountains, which also functions as a wind blocker for the North West cold wind.
Extensive green roofing for the flat roof of the shelter, which uses local small plants that could survive strong winds.
2015-13 Mountain view bus shelter2-small 2015-13 Mountain view bus shelter-small


Thermal Performance of Curtains, and other retrofit options

A couple common questions:
“What is thermal resistances of window film with an air gap, and curtains?”

  • Timber framed window, single glazed (baseline)
    • R0.2
  • Timber frame, single glazed, with drapes and pelmet
    • R0.3 $0-$150/m2
  • Timber frame, single glazed, with window film
    • R0.4 $5/m2
  • Alu frame, thermal break, double glazed, low-e
    • R0.4 $450/m2
  • (Higher R values mean less heat loss)

“What are good retrofit options for my home”?
Reducing heat loss is one important strategy.  (Another is maintaining ventilation)
Good strategies mean picking the most reduction in heat loss, for the least cost.  This chart can help.

Bishop, T. W. (2009). Heat Losses and Gains in Residential Housing in Southern New Zealand (Thesis, Master of Science). University of Otago. Retrieved from


Nine single person units built by young homeless people for themselves

“The project was for 9 single person homes on a small plot adjacent to a disused canal in Peckham – to be self built by local young people in housing need. The build was linked to a local training centre where the self builders were trained up to NVQ level 2 Carpentry and Joinery.

Consortium, a local umbrella group of housing charities, employed a worker to research the project and get it off the ground. This worker stayed on for the build process and acted as a support worker to the self builders. The site was managed by a full time site/project manager who had built on a previous self build scheme and who had youth work experience.

On completion of the scheme the builders became tenants of South London Family Housing Association, who had acted as development agents for the project

A very thorough and honest review report on the project is available from CSBA”

Source: Consortium


BSHF | Learning from informality

The cities of the future, which is what many urbanism conferences talk about, those cities that grow fastest, are not constructed out of glass and steel, but out of straw, recycled plastic, scrap wood, and bricks made of construction waste. Housing there isn’t built by the building companies, developers and policy makers who attend the conferences, but by people building for themselves.

Source: BSHF | Learning from informality


Temporary projects leave long-lasting legacy

The temporary projects which popped up on newly vacant land around Christchurch after the earthquakes have a lot more value to a traumatised public than we may think.Dr Andreas Wesener, a lecturer in Urban Design at the School of Landscape Architecture has just published research on transitional community-initiated open spaces (CIOS) in Christchurch and says they have a range of benefits that might strengthen community resilience.His paper discusses benefits, possible long-term values and future challenges for community-initiated temporary urbanism in Christchurch.“Resilient people have been described as being able to find positive meaning and display positive emotions even in times of crisis, and introducing positive stimuli and engaging in positive activities have been considered vital in distressing post-disaster situations,” Dr Wesener says.There is evidence that people’s participation in temporary projects has encouraged positive emotions and creativity, strengthened social capital, such as community gardens, and fostered community empowerment within a challenging post-disaster situation, he says.“On an individual level, community members who lost jobs in the aftermath of the earthquakes reported that working on temporary projects had provided opportunities to cope with post-traumatic stress, remain active, learn new skills, establish new networks and in some cases job opportunities have been created.“Even passive passers-by without direct involvement in community-led activities may experience positive emotions solely by noticing that ordinary people are recreating and rebuilding structures within a destroyed urban landscape.”
Source: Temporary projects leave long-lasting legacy