Category Archives: thermal mass

Around the World in Eight Designs: Part 12

At the end of the last column I promised to include some more examples of thermal mass this week along with a photograph. As a reminder, thermal mass is part of the trilogy for passive solar design, which also includes solar gain and insulation.

Thermal mass absorbs heat from sunshine slowly during the day and then releases it at night. In this way it is a bit like the opposite of a night store heater, which stores cheap electric heat at night and releases it throughout the morning.

In modern houses, thermal mass can take the form of an insulated concrete foundation slab, but retrofitting a 100 year-old villa is a different story. Because an old villa has a raised floor (ie, built on piles) adding thermal mass inside of the thermal envelope is more of a challenge. During the renovation of our villa we added mass in three ways.

The first and easiest way we added thermal mass was to add a layer of plasterboard (aka “Gib”) to a number of north-facing internal walls that receive direct sunlight during the winter months. If you have ever lifted a sheet of plasterboard you would know it contains lots of mass. In other words, it’s heavy.

The next way we added mass was to install an iron claw foot bathtub in our northwest-facing bathroom. Like the extra layer of plasterboard, the iron slowly absorbs the sun’s warmth during the day and releases it at night.

Finally, and most dramatically, we installed an old Shacklock 501 cooker in the kitchen. The placement of the Shacklock ensures that it receives direct sunlight three times a day through three different windows during winter. The cooker weighs 300 kg, and is surrounded by another 300 kg of bricks. The insulated hearth accounts for another 100 kg. Screen Shot 2015-09-07 at 12.07.04 pm

All in, the 700 kg heater/cooker works great as thermal mass during sunny winter days. It moderates the kitchen from overheating during the afternoon and helps ensure the morning temperature is a little higher than it would otherwise be.

Oh, and on cloudy days we stoke the Shacklock with wood and cosy up with a big pot of soup on top and a loaf of bread in the oven.

Around the World in Eight Designs: Part 11

Editor’s Note: This is part of the continuing series on good home design from around the world.

 

In the last column I wrote about adding glazing to the northern side of an old, run down villa to increase the amount of free solar heating during the winter. Specifically, we made three of the windows larger and added French doors. At the same time, we reduced the amount of south-facing glazing by removing two windows and replacing them with insulated walls.

These steps were part of the process of creating a passive solar home while drawing on many of the examples of good home design that I have seen all around the world.

However, one of the main problems with passive solar design over the last four decades has been homes that overheat during winter because of too much north-facing glazing and not enough thermal mass. Thermal mass is the least understood aspect of passive solar design. I’ll do my best to explain it by comparing it to a rechargeable battery, but first some background.

During the 1970s some very well meaning hippies started building homes with heaps of glazing but overlooked the inclusion of thermal mass. The homes overheated during sunny winter days and the occupants had to open windows to let out some of that heat.

Here is where the battery analogy comes in. Thermal mass absorbs the extra heat (energy) during the day and stores it like charging a battery. Think of a curb or concrete stairs that have been in the sun all day long and retain some of that heat after sunset. If you touch them they are warm after the sun has disappeared.

To get an idea of what thermal mass is, think of water and anything that sinks in water. These things are “massive,” or in other words dense. In a home, common forms of thermal mass are concrete, bricks and tiles.

But don’t be confused by a home with brick cladding or stucco. The thermal mass must be inside of the home, not outside. Specifically, it must be inside of the building envelope, which includes the stud walls, windows and doors.

Another key aspect of thermal mass is that it should be struck directly by sunlight to be most effective. In the same way, rechargeable batteries work best when the charger is plugged into the power point!

With plenty of north-facing glazing and ample thermal mass, instead of overheating during a sunny winter day, the excess sunlight energy is stored in thermal mass during the day (charging the battery) and then slowly released at night as the home cools (discharging the battery). I am partial to thermal mass as a design element because there are no moving parts, and it effortlessly takes excess heat energy at one part of the day and tucks it away for another part of the day, or rather the “middle of the night.”

I hope that helps explain how thermal mass works. In the next column I will give some more examples.

 

Peace, Estwing

Around the World in Eight Designs: Part 2

 

Editor’s note: This is the second of an eight part series.

 

Last week I introduced the concept of passive design using the ancient cliff dwellings of Mesa Verde (Colorado, USA) to illustrate the point. In a nutshell, the “Ancestral Pueblo Peoples” – also known as the Anasazi – chose certain cliffs that excluded the hot summer sun but welcomed its warming rays in winter.

The Anasazi first occupied the caves over 1,000 years ago. Warm in winter and cool in summer: they were no dummies. Here is what we can learn from them: design for the climate; use local materials; harness free energy.

During the 1970s as small group of hippies used these same design principles in the same region of the US Southwest but in a radically different way. Using beer cans, old tyres and soil, they built what they called Earthships. Here is what Wikipedia has to say:

“An Earthship is a type of passive solar house that is made of both natural and recycled materials (such as earth-filled tires), designed and marketed by Earthship Biotecture of Taos, New Mexico. Earthships are constructed to use available natural resources, especially energy from the sun. Earthships are designed to use thermal mass construction and natural cross ventilation, assisted by thermal draught (Stack effect), to regulate indoor temperature.” Screen Shot 2015-06-11 at 6.53.27 am

Both the Anasazi and the hippies figured out ways to live comfortably in a climate that ranges from 40 degrees in the summer and minus 10 in the winter by using passive design. An Earthship is designed to allow low angle winter sun to reach deep inside the structure but to exclude high angle summer sun. Once the winter sun enters the structure some of it is stored in what is called thermal mass, such as an earthen floor, bricks, tiles and even the earth-filled tyre walls.

Believe it or not, thermal mass is essential for keeping these structures from overheating in the middle of winter on cold, sunny days when the temperature outside is right at the freezing point. Thermal mass acts as a battery in that it stores excess energy (in the form or heat) during the day and releases it at night. Of course the Earthships also contain plenty of insulation to hold that heat inside the structure overnight. Screen Shot 2015-06-11 at 6.53.11 am

All of this falls into the category of passive design because it requires no moving parts such as fans or pumps, or the electricity to run them. Passive means it just happens by natural energy flows and cycles.

Earthships also employ passive cooling systems, but I see I am out of words for this week and next week’s column is all about passive cooling with examples from the tropical nation of Nicaragua.

 

Peace, Estwing

Equinox: Honoring the Sun

Screen shot 2015-03-21 at 7.02.24 AM

We’ve reached the autumnal equinox and there is probably not a person in the city that would not say what a glorious summer we have had. Plenty of sunshine, light winds, and, after an initial dry spell, enough rain to green up the pastures and the garden.

But, like it or not, summer will come to an end, and the equinox is a reminder that we are tipping toward winter with the hours of daylight becoming shorter than hours of darkness for the next six months. It is also a timely reminder of how valuable the sun is to life on earth, and what a difference its absence can make.

But like every great Achilles, Solar energy has its heal: it only works when the sun is shining on our side of the planet. I often use a solar cooker as a way to engage people in conversation about the potential for sunlight energy. Inevitably someone will ask, “What happens when the sun isn’t out.” Screen shot 2015-03-21 at 7.02.14 AM

Sadly, no one has yet to invent a lunar cooker, but there are many ways to store solar energy overnight and even for a number of cloudy days in a row. With solar cooking, the best place to store it is in your belly, but other solar storage systems include batteries, water and concrete.

Batteries are often used to store electricity generated by photovoltaic (PV) panels in places not served by mains power. Whether it is a yacht at sea or a bach in the wop wops, these situations are often called, “off-grid.” The “grid” refers to the network of power lines that serve the vast majority of us.

Obviously, off-grid housing is not vulnerable to mains power interruption, and is therefore valuable for emergency preparedness. Even though our rural home is served by mains power, I am designing a hybrid PV system that will heat our water most of the time but also have a small battery bank for emergency lighting, water pumping, radio and mobile phone charging.

Without meaning to offend anyone’s intelligence, a traditional solar hot water system stores sunlight energy in the form of heated water. The energy itself (heat) is stored inside of an insulated cylinder overnight. Depending on the amount of insulation around the cylinder and a household’s hot water use, the supply can last for three or four cloudy days. Solar hot water would also be a treat in the case of a prolonged mains power outage. Screen shot 2015-03-21 at 7.02.38 AM

Sunlight energy stored in an insulated concrete slab is called “thermal mass.” Like solar hot water, the heat is stored overnight and potentially for a number of cloudy days in a row. For any new home being built in New Zealand, passive solar design is an affordable approach to a high performance dwelling. Additionally – you guessed it – a passive solar home would serve its occupants very well during a mid-winter power failure if their only heating sources relied on electricity such as a heat pump or plug in heater.

Finally, don’t make the mistake of thinking that solar cooking is only a summertime endeavour. We have cooked through the last six New Zealand winters with great success. Memorably, during the week-long cold snap in August 2011 when we had snow flurries in Majestic Square, I managed to burn a pot of rice and a curry on the very same day. That is solar power. Screen shot 2015-03-21 at 7.02.46 AM

Peace, Estwing

Keep Calm and Think Different: It Takes Money to Save Money, Part 2

Screen shot 2014-10-10 at 8.10.02 PM

Last week I introduced a new variation on an old adage: it takes money to save money. Of course this idea is not new to most people, nor is it new to this column, which has focused on the concept of ‘payback period’ since it was first published two and a half years ago.

But this concept is long overdue for the New Zealand housing sector that is known for high running costs and low performance. According to Nick Collins, the CEO of the housing performance research organization Beacon Pathway, “Much of New Zealand’s existing housing is cold, damp and unhealthy which leads to poor social and health outcomes. Poor quality, poorly performing housing affects residents’ health, education and quality to life, the resources we use, and general community wellbeing.”

I would suggest Collins’ words describe the situation in Wanganui to a tee, yet this issue does not seem to get significant traction in our community. As a self-described “struggling provincial economy” it astonishes me that, ‘zombie-like’, we voluntarily send millions of dollars to power companies in Auckland, Wellington and Christchurch every year when we could easily retain them in our community.

Maybe it comes from growing up alongside the dying city of Detroit, or maybe it comes from being an under-sized gridiron (American football) player, but I have always made it a point to stand up for the ‘little guy.’ I hate waste and I like supporting local businesses.

The process of renovating our villa in Castlecliff ‘stimulated’ the local economy to the tune of $35,000. This total sum will be ‘paid back’ through energy savings and low maintenance costs over the course of about 12 years. The exceptional level of sustainability of this property can be explained through exemplary levels of energy efficiency, long-term durability of products, and the high productivity of fruits, veges and fowl. The entire property has been designed and managed to be low-input and high performance, ie, it takes money to save moneyScreen shot 2014-10-10 at 8.09.50 PM

As regular readers are aware, the villa was redesigned and renovated as a passive solar home. Between April and August, morning sunlight reaches deep into the structure, bringing warmth inside early in the day when the temperature is lowest. An abundance of glazing on the northeast and northwest sides ensure that free sunlight energy heats the northern parts of the home on most winter days to 20 – 25 degrees.

Throughout the day some of the sunlight energy is absorbed within thermal mass, ensuring that the interior does not overheat while storing the excess warmth overnight when it is released into the home. This extra thermal mass takes the form of a second layer of Gib on the walls, a cast iron claw foot bathtub, and a multi-fuel cooker with brick surround. When the sun is not shining, the multi-fuel stove easily heats the northern part of the home to 20 degrees or above on a few sticks of wood, with the added benefits of cooking and baking.

Two-thirds of the home is easily heated by this combination of sunshine and a small amount of firewood. (The southern bedrooms are kept cooler as is common in most Kiwi homes.) A super-insulated building envelope ensures that much of the heat remains in the structure overnight. Temperature in the lounge, kitchen and bathroom rarely drops below 14 degrees overnight with no heaters running. Some of this energy performance can be attributed to a combination of double-glazing, pelmets, and floor-length lined curtains, Roman blinds and window blankets. This combination of window treatments performs to a level of triple-glazing or better.

Screen shot 2014-10-10 at 8.09.39 PM

Other energy-efficiency measures we used in the home were Energy Star appliances, compact fluorescent light bulbs, and solar hot water. This combination meant that our power bills over the last year ranged from $17 to $35 per month. Contrary to what some of our critics claim, we do not sacrifice comfort or convenience. Solar hot water allows us to take long showers even in winter, while our appliances include the following: refrigerator, freezer, oven, toaster, electric kettle, cake mixer, wizzy stick, wifi, alarm system, clocks, radios, power tools, etc.

How’d we do it? By thinking different: it takes money to save money.

Peace, Estwing

Would You Buy This House? Part 1: Energy

Sustainability at 10 Arawa Place

The exceptional level of sustainability of this property can be explained through exemplary levels of energy efficiency, long-term durability of products, and the high productivity of fruits, veges and fowl. The entire property has been designed and managed to be low-input and high performance.

Screen shot 2014-09-06 at 8.04.05 AM

Part 1: Energy Efficiency

10 Arawa Place has been redesigned and renovated as a passive solar home. Between April and August, morning sunlight reaches deep into the structure, bringing warmth inside early in the day when the temperature is lowest.

Screen shot 2014-09-06 at 7.59.58 AM

An abundance of glazing on the northeast and northwest sides ensure that free sunlight energy heats the northern parts of the home on most winter days to 20 – 25 degrees. Screen shot 2014-09-06 at 8.01.59 AM

Throughout the day some of the sunlight energy is absorbed within thermal mass, ensuring that the interior does not overheat while storing the excess warmth for overnight when it is released into the home. Beyond the mass already in the structure, we added approximately one thousand kilograms of thermal mass that receives direct winter sunlight from sunrise to sunset through three large windows and the French doors. Screen shot 2014-09-06 at 8.00.21 AM

This extra thermal mass is essentially invisible because it takes the form of an extra layer of Gib on the walls, a cast iron claw foot bathtub, and a multi-fuel cooker with brick surround. When the sun is not shining, the multi-fuel stove easily heats the northern part of the home to 20 degrees or above on a few sticks of wood, with the added benefit of cooking and baking.

Screen shot 2014-09-06 at 8.00.30 AM

Two-thirds of the home is easily heated by this combination of sunshine and a small amount of firewood. (The southern bedrooms are kept cooler as is common in most Kiwi homes.) A super-insulated building envelope ensures that much of the heat remains in the structure overnight.

Screen shot 2014-09-06 at 8.01.46 AM

The walls in the northern parts of the villa are insulated to R-2.8 and the ceilings are insulated to R-3.6 above the kitchen and bathroom and to approximately R-5 above the lounge and all three bedrooms. These all far exceed the building code. (The underfloor insulation is incomplete at the moment.)

Screen shot 2014-09-06 at 8.00.10 AM

We spent two winters in the small bedroom and never used a heater. Our body warmth alone kept the room above 15 degrees all night long. Temperatures in the lounge, kitchen and bathroom could drop to 14 or maybe 13 on the rare morning with a frost. Some of this strong energy performance can be attributed to a combination of double-glazing, pelmets, and floor length lined curtains, Roman blinds and window blankets. This combination of window treatments performs to a level of triple-glazing or better. Screen shot 2014-09-06 at 8.02.07 AM

Other energy-efficiency measures we used in the home were Energy Star appliances, compact fluorescent light bulbs, and solar hot water. This combination meant that our power bills over the last three years ranged from $17 to $31 per month including the daily line charge. The appliances we operated were: refrigerator, freezer, oven, toaster, electric kettle, cake mixer, wizzy stick, wifi, alarm system, clocks, radios, power tools, etc. Screen shot 2014-09-06 at 8.02.16 AM

The solar hot water system is set to a winter sun angle to maximize performance when hours of sunlight are shortest. The 240-litre tank allows ample storage to bridge three winter days without sun. We placed the temperature monitor in the hall next to the bathroom so it can be easily referenced. Over three winters, we only turned on the electric boost for the hot water a handful of times for 20 to 30 minutes each.

Screen shot 2014-09-06 at 8.01.28 AM

To be continued…

 

Part 2: Durability

Coloursteel Maxx roof, November, 2011.

New, low-maintenance exterior cladding, 2012.

High quality exterior paint.

Walls braced against earthquake and wind.

Sistered bearers and joists fro added strength under floor

All floors treated for borer

All new wiring, November, 2011

Capping on fences to protect end grain from rain

Wind-hardy trees to protect netting from long-term UV damage

Earthen pizza oven protected from rain and wind

Brick patio instead of wooden deck

Driftwood – durable native hardwood timber for landscaping

 

Part 3: Productivity

Topsoil: 6 cubic metres for garden beds, trees and top-dressing lawns.

Wind protection: double-layer of wind cloth with new treated posts.

Rainwater collection

Compost: 8-10 cubic metres.

Native plantings for privacy and wind protection.

52+ Fruit trees: 7 feijoas; 11 olives; 13 apples; 5 peaches; 3 plums; 1 apricot; 2 guavas; 4 grapevines; 2 figs; 1 banana; 1 tamarillo; 1 orange; 1 loquat; plus rhubarb, cape gooseberry, strawberries, summer and autumn raspberries,

Vegetable gardens:

Rotational grazing of ducks and chooks:

 

 

 

It is Heavy, It’s Thermal Mass

A decade and a half before Paul Simon’s innovative album Graceland (1986) exposed Western listeners to unique and original African sounds and rhythms, the incomparable Neil Diamond did the same with the lesser known album, Tap Root Manuscript (1970). Side two of the album is called “The African Trilogy (A Folk Ballet),” and includes two of my all-time favourite Neil Diamond songs: I Am the Lion, and Soolaimon.

Screen shot 2014-05-23 at 6.37.14 PM

 Side one, however, is more likely to be memorable for most people due to a series of Top 40 (US) hits: Cracklin’ Rosie; Free Life; He Ain’t Heavy, He’s My Brother. The last of these hits – He Ain’t Heavy, He’s My Brother – was ‘recycled’ from The Hollies, whose version reached No. 1 in the UK Singles chart in 1969.

Like this well-known song, our Shacklock 501 is: a favourite feature of our home; it is ‘recycled’ from another dwelling; but critically, it is very heavy. And that is the point.

 Screen shot 2014-05-23 at 6.32.13 PM

Along with acting as a heating source for our home on cloudy, cold winter days, the 700-kilogram coal range/brick surround/concrete and tile hearth acts as a ‘heat sink’ on sunny winter days. In this respect, the combined heavy stuff that makes up the building code approved unit functions as ‘thermal mass.’

Screen shot 2014-05-23 at 6.32.04 PM

From a purely physics perspective, everything that has mass can absorb heat. In the extreme, air has mass so it can absorb heat. But ‘light’ things like air gain heat quickly and lose it quickly. ‘Heavy’ things, on the other hand, absorb heat slowly and release it slowly.

Water is a good example of a substance that has significant thermal mass. One of the main reasons that Whanganui has such a wonderfully temperate climate is because the Tasman Sea is a giant heat sink. While Palmerston North experiences higher highs and lower lows than our fair city, we remain comfortably in between. That is one reason we all love living here.

When I teach eco-design, I make these general statements for people to wrap their heads around:

Water and anything that sinks in water has good thermal mass, but anything that floats in water acts more as insulation. The faster something sinks in water the more thermal mass it has, and the higher something floats in water the more insulation it probably provides. Think polystyrene. 

At its heart, a good song serves multiple functions: it moves people with its beat; it engages people with its lyrics; it rewards its writer with financial success.

Designing for multiple functions is at the heart of good eco-design. A clear example of this is the placement of the Shacklock 501 at the heart of our home.

 Screen shot 2014-05-23 at 6.32.46 PM

The 700 kilogram heating unit is situated approximately at the centre of our living spaces – lounge, kitchen, dining – so that the heat can radiate in all directions. While this may seem like common sense, a quick trip down Polson Street in Castlecliff may surprise you: at least four out of five chimneys are built on an exterior wall. Screen shot 2014-05-23 at 6.32.35 PM

As you can see from the photos, our Shacklock is built along an interior wall next to French doors that lead from our kitchen/dining to the lounge. Additionally, this location allows the sun to strike it three times during each winter day: morning, mid-day and afternoon.

Screen shot 2014-05-23 at 6.32.23 PM

Like the Tasman Sea, the Shacklock’s thermal mass is a temperature moderator powered by sunlight energy. But, in the event of a day or two without sunshine, we can always load it with wood, which is really just sunlight one step removed.

Peace, Estwing