Pittsburgh, the steel city, has a reputation as a place of giant steel mills belching coal soot. It was certainly that way for much of its history, however those mills are long since closed, and Pittsburgh is now part of what is called the rust belt. As such, it has had to work to reinvent itself. I can't say I'm entirely aware of the direction in which Pittsburgh is heading, but it is a pleasant place to visit.
One of the highlights for me was our visit to the Phipps Conservatory and Botanical Gardens. Anytime I come across a botanical garden, especially one with a conservatory, I make it a point to check it out. While a wood nerd for sure, I'm also a bit of a plant geek, though I must confess to vast amounts of ignorance in that regard. I've been to several famous botanic gardens, and I have to say that Phipps is among the best in the country, if not the world. The conservatory is incredibly vast - too much by far to take in in one day. The current exhibit featuring Plants of the Congo was incredibly fascinating, and the rooms with cacti on exhibit simply blew my mind.
Phipps seems to have adequate funding, unlike many public institutions in the US, and has set a mission for itself to be on the cutting edge of sustainable operation. The new conservatory which houses the plants of the Congo exhibit, for example, is net zero energy - pretty impressive for what otherwise is a large glass and metal box.
A recent construction at Phipps is the Center for Sustainable Landscapes. Here's a video put out by Phipps which showcases the building and their forward-thinking approach:
It was a pleasant building to be in - just a nice temperature, cooler than outside yet quiet and peaceful with no a/c system going.
A display in the structure which caught my eye was that of a model section of the building wall, which featured an innovative insulation material, called BioPCM (which stands for Bio Phase Change Mat). This is a type of building envelope material featuring a new (to me) application of a technology, namely phase change material.
BioPCM is configured as a plastic sheet with small pillows filled with soy-based gel:
From the manufacturer:
Phase change materials “PCMs” use a basic nature of physics, the absorption or release of heat when matter changes from one state to another, to aid in thermal storage. When you warm up a solid material, its temperature rises steadily until it nears its melting point. Then it absorbs a significant amount of heat, but the material does not get warmer, until it fully melts. The process of changing phase from solid to liquid absorbs an enormous amount of energy comparatively to when the material's temperature is changing in either its liquid or solid state. When you cool down and freeze a liquid, the same process happens in reverse, the temperature remains at the freezing temperature until a significant amount of heat is removed, releasing stored energy and allowing it to freeze (change phase from liquid to solid). This physical interaction with the building environment is beneficial by absorbing excess heat and cooling the space and then releasing this stored heat back at a later time as the temperature drops below the product's Q factor/desired temperature.
There's a lot to like about this product. It is lightweight. It is made in the United States. It is low-tech and passive. It is made from rapidly-renewable and sustainably harvested non-food soy and palm oil byproducts as well as other rapidly renewable plant materials including coconut and soy. It can meet class A and C fire ratings. It can meet class I, II, or III perm ratings. It works when it is hot outside to keep the building cool, and it works when it is cold outside to keep the building warm. It can be directly applied to conventional light framing with studs 16" on center as a material supplemental to conventional insulation. It does not add significant thickness to a wall. It would not add appreciable weight to a ceiling or roof. It can be used in new builds or retrofits.
Here's a typical installation:
(Image from http://gsdmaterialscollection.tumblr.com/post/13110785188/phase-change-materials)
As noted above, this material is not really insulation as such - it behaves more like a thermal mass wall. The pillows are, in other words, latent heat storage units, engineered to change phase at room temperature. Instead of 12" (say) of concrete or cob, you only need a thin layer of BioPCM to achieve the same sort of thermal mass effect, where the wall absorbs and releases heat at a rate slower than environment. So, while the outside temperature may cycle up and down in a fairly large range, the phase change material causes the interior temperature to only cycle up and down a minor amount, as this graph shows:
(image from the manufacturer's website)
The 'control' in the above test was an identical structure with a conventional insulation system. The test structure had only one difference in build: the addition of BioPCM. As you can see, with phase change material, the interior temperature only moved through a 4˚ swing while ambient temps varied by 37˚. What this means for the occupants is a more comfortable living/working environment and greatly reduced HVAC costs. One would think that based on the above facts alone, over just a few years the phase change material would easily pay for itself.
BioPCM can easily be combined with other types of insulation materials in a wall or roof - even in floors.
What about durability? Well, the company has had it tested with a temperature cycle that is quite severe by any standard:
- Begin at 20°C
- Ramp to -20°C 5 minutes
- Hold -20°C 20 minutes
- Ramp to 60°C 10 minutes
- Hold 60°C 20 minutes
- Ramp to 20°C 5 minutes
They cycled the material through 23,563 cycles, the equivalent of 87.2 years. When retested for thermal efficiency, the material showed little to no breakdown. Such a long service life means that the payback period for the investment will be relatively short.
So, that looks pretty cool to me - not withstanding the word play. Not sure about pricing of BioPCM, however a few of the green building sites out there were using terms such as "finally there is an affordable phase change material"....
While in Pittsburgh we also took in some interesting architecture - the subject of the next post.
Thanks for visiting the Carpentry Way.