Bruce Hammond Interview with Claudia Cleaver (REC-USGBC)


1.The science and practice of green building has changed since you first built your own sustainable house at Oak Springs so many years ago. What are the most exciting changes you see in the field and what would you change about your own house?

Sustainable building practices and opportunities for green construction solutions have come a long way in the last 25 years. The US Green Building Council has done much of that heavy lifting through the development of, the education on, and the application of the LEED standard across all classes of building types and the multiples of buildings in their campus wide application of the LEED standards.

Broad and deep technical developments have come to market and bright and creative engineering & design professionals have brought forward important new directions like the Passive House Standard, Zero Net Energy homes, building materials ratings & certifications, material de-carbonization strategies, and important integrated methodologies like the “Living Building Challenge” have come into more widespread understanding and application. These are potentially world transforming bodies of knowledge, if applied more and more broadly.

What has worked well and what have you or would you like to change about the home at Oak Springs.

The house at Oak Springs I built in 2000 as a clear example of integrated green design and construction and was inspired by residential design examples I saw at the first NAHB Green Building Conference in Denver Colorado in 1999. Following that I had the opportunity to dive into conversations with the George Beeler AIA, a highly creative and skilled local green architect. Inspired by his use of design phase energy modeling,  the use of trombe walls, and the sustainable concrete mixes he had employed in the design of the Environmental Technology Center at Sonoma State University, George assisted me with consultations to integrate these sources of inspiration into the development of our home.

I had already built passive solar homes prior to that time and found those principles easily integrated into the Oak Springs design process as the key drivers, envelope, orientation, thermal mass, good glazing, and well planned roof eave overhangs. The house was a great and very energy efficient building and a well-rounded example of the deployment of each of the parts of integrated green design; sustainable site development, water conservation, energy efficiency, materials and resource conservation, & indoor environmental quality. It is also a very comfortable home year round, based on the implementation of fundamental active and passive solar design strategies.

To get the the tight envelope and high thermal performance of the envelope I made use of structural insulated panels ( SIP’s) which are made with high embodied-energy virgin hydrocarbon sourced polystyrene foam insulation material. Many other options for well insulated building envelopes are available as alternates to this approach currently and in other projects since Oak Springs we have moved more and more toward those so as to reduce the use of foam insulations and the hydrocarbon use associated with them.

2.You have completed many green houses in your career. What have been some of your favorites and what was it about them that you especially liked? What would you have made better?

These 3 homes readily come to mind out of many-

Sonoma Valley Straw Bale HomeLEED Platinum Award – USGBC

This project was awarded “Home of the Year” from Green Builder Magazine for excellence in Site Integration. This resulted from clients who loved the land where their home was built and the close conversations among the landscape architects, Sentient Landscape Design, and the owners and the overall design team headed by DSA Architects. As a gardener myself since a young age the most satisfying thing for me following a construction process is to see and experience the re integration of a construction site into a lovely tended natural landscape – nesting the home into its surrounding environment and creating spaces for the many layers of native species once again. This project accomplished that amazingly well.

The project also enjoyed solid support from the owners for a truly integrated design team approach in it’s design and construction development process. Regular meetings to analyze and develop layered solutions to all areas of the design while integrating feasibility and budget ramifications made for a challenging but very satisfying process overall.

Nicasio Passive Solar –

This project had a variety of innovative green design technologies employed throughout and was designed by Schwartz + Associates. Notable was the use of an “Ice- house roof” design which placed a corrugated corten roof surface above a ventilated space as a kind of heat deflecting shield above the entire roofed area. This considerably lowered high summer temperature effects on the building. There were integrated thermal controls to share heat from the solar hot water panels at the house with the swimming pool in the summer. Much of the materials from an earlier home and barn were salvaged for reuse.

There was a down-side that arose due to the less than perfect ability of design stage thermal modelling to predict actual built performance.  The home was heated hydronically using an air sourced heat pump which ended up being under powered for the actual heating demands due to the large window areas and high thermal mass. This resulted in difficulty raising the inside temperature if it fell below 60 degrees in the cold season. The heating system design was later modified for better performance.

Petaluma Health Sanctuary –

This project also resulted from a very well engaged design development process focused on integrated solutions for a client with severe multiple chemical sensitivities. The result has created a “safe haven” for him. Working with Paula Baker Laporte, a noted green architect with a focus in the field of healthy homes, we worked over a 6 month period in the early design phase to vet best practices & solutions and overall materials compatibility for this client.

We eliminated underfloor crawl spaces in favor of a “waffle matt” structural slab foundation to avoid any condition which might develop mold. The structure of the home was build with Faswall blocks – an eco friendly insulated concrete forming system made from recycled pallets with a core of reinforced poured concrete. Finishes over that were natural haudraulic lime plasters, American Clay plastered walls at the interior, natural paints, exposed radiant heated concrete floors and a sophisticated Zehnder heat recovery ventilation system with additional micro filtration at the air intake and a recirculation setting for fire season protections. All this was done as a budget driven process and was quite challenging but also very satisfying overall.

Occidental Straw Bale –

This is a current project and is very satisfying as an example of well integrated green design and construction. It is a passive solar design by Arkin Tilt Architects and has a focus on the decarbonization of materials. We developed a very low Co2 emissions slag-cement concrete mix design that is tailored to this project. The project uses a combination of rammed earth blocks, double offset 2x framing, and straw bale for its wall systems. The framed walls and overhead cathedral ceilings are cellulose insulated with an exterior Gutex insulation layer overhead. We employed a thorough air sealing approach throughout the building and have an air to water heat pump system for the hydronic heating in the floors.  The on-site stormwater management is accomplished by using a natural landscape approach that employs several large underground water infiltrators below the dry stream surface features. The overall planting and site design was by Sentient Landscape.

3.Has your emphasis changed in creating a green residence? Do you focus on other things now?

These elements of building construction and management are in my attention always these days –

Durability still remains primary – let it all last as long as possible through the right materials selections installed correctly and with thoughtful care.

Envelope air sealing and how to do it thoroughly but economically- Learn that well and the conditions where it is appropriate and needed. Learn about moisture/ vapor diffusion and where it is appropriate and needed.

-Embodied Carbon – Collectively we have a pretty good handle overall with operational carbon impacts in the built environment in the US ( mostly). Now our use of high embodied energy materials needs very careful scrutiny and cost/benefit analysis.

1) We need to reduce the pounds of Portland cements in each cubic yard of concrete to the absolute minimum while still getting good durability and performance.

2) Design less concrete volume into the project to begin with.

3) Avoid steel based structural solutions where at all possible in favor of wood LSL’s / LVL’s / Glu lams etc.

4) Use the best glazing system possible (and the least of it possible too !)

5) Avoid hydrocarbon based foam insulations in favor of natural materials, cellulose, and wood based board insulation materials like Gutex.

Quality Control -with materials, subcontractors,  the construction crew and at all levels is an ongoing critical concern which needs attentive care.

-Budgets -meeting client budget goals – considering various options for a solution.

-Communication- There is no substitute for good, skillful, timely communication.  To the clients, to the design & engineering groups, to vendors, to subcontractors, and to the construction team. Regular meetings  are key !

Do you use any rating systems now – LEED, Build it Green, Passive House etc?

With tight budgets currently, even with building at the high end of the marketplace, the added cost of a LEED rating has not been a priority for recent clients, even on some otherwise deep green projects. We have done LEED Gold and LEED Platinum projects, as well as several Green Point Rated homes over the last 20 years.

 Have you found California’s T-24 energy code and Calgreen helpful in pursuing green building? What else is needed?

California’s T-24 energy code is a leadership standard that continues to evolve and to pull other state’s codes along with it, which is great. But even though it is a high bar, it is still the minimum standard and should be overshot as much as possible on each project. That is always a result of a wise integrated design approach and does not happen by adding technology and solar panels after everything else is established through a completed schematic design. It needs to enter the design from the start.

Cal Green is similar, and focuses us all on managing resources efficiently by the documentation of waste that is generated through construction, which is an enormous issue. Our recycling efforts and closing resource loops in the supply chain is largely un-addressed in the marketplace. More needs to be done through consumer education and regional and municipal advocacy to close loops and illustrate alternative approaches & materials uses. Manufacturers also need to re integrate waste materials into new products.

Do you find cost an impediment to creating a green residence?

Green building does not “cost more”- poor and unskillful planning costs more ! There are clear examples of very green “production homes” done in the central valley as low-cost housing. Designing a green home needs to be  undertaken right from the very start of design and a realistic budget needs to be set. To be truly useful and not cause client disappointment and project disruption following a completed design those budgets need to be current.

They need to clearly and separately distinguish the “soft costs” of architecture fees, engineering consultant fees, a builders pre-construction consulting services and permitting fees. They also need to separate Site Development and direct Construction costs. A responsible budget will inform the client of all these commitments up front, since the “construction cost per square foot” numbers that get thrown around are mostly very vague about what is included. This takes several rounds of focused work starting from a rough order of magnitude budget work up, based on past projects, and then working toward a clear and focused final construction budget based on actual project specific take offs and subcontractor proposals. That can make all the difference to correctly set client expectations and a project’s success right from the start.

What trade offs do you run into?

Quality of material selection is the most extensively adjusted element in all project budgets. With so many budget line items in a construction project each one can be inflected toward higher or toward lower quality/cost.

People most often focus on bringing down the highest individual budget numbers and yes, that is important, but the incremental costs of cabinetry and shelving, tiled areas, plumbing and lighting fixtures can really add up to a large number so they are worth looking at carefully. Windows and doors are commonly adjusted in a budgeting process. Paying for fewer high performing windows is better than many lower quality ones and will most likely save energy and possibly even overall cost.

For example – Higher quality windows and good building orientation will lessen the costs of a mechanical system and the long term building maintenance and energy costs.      This is a big and complex topic J

6.What is your experience with;

Straw bale- We have used straw bale in 2 high quality homes and consider it a great carbon sequestering enclosure/ insulation solution. As a locally available natural material it is at the top of the list for an ecologically appropriate building material.

Bamcore – We have not built using the Bamcore system, though I have known about it for many years. I consulted with the original engineer and development team to direct their attention out into the green building community for connections with resources and to gain necessary attention . They have gained a lot of funding and standing at this point and I am glad for that. Bamboo construction has most of the best attributes of straw bale and can be a good structural material as well.

Exterior insulation- We have done several projects where an exterior insulation layer has been incorporated. These are multilayered systems and need to be done carefully so that the shell lasts well and insect entry is controlled. Breathability and vapor open conditions need to be well considered. Our climate region is mostly very forgiving.

Panelized construction – We have used panelized construction on a couple of projects over the years. There are many versions; from rough framing and shearwall only, to versions that are completely detailed and finished walls with plumbing and wiring in place. To use it successfully is always a matter of pre planning well and the timing of the order so that the start of construction is not delayed once the foundation is ready for the building construction.

Favorite window manufacturer – Loewen!

Heating cooling systems- SpacePak air to water heat pump systems for hydronic heating  – also  -zoned air sourced heat pump systems

Insulation types – Blown in cellulose, Gutex board insulation, Roxul mineral wool

Do you have special favorites or anything you are excited about –

Cross Laminated Timber (CLT) ! –  Carbon sequestering structural system with finished interior wood walls and very few overall pieces in the shell of the building- a prefabricated shell. The aesthetics and relative simplicity of this system is very appealing system to me. I look forward to seeing this more widely deployed in residential construction.

6. Are you hopeful that we can make significant climate response through green building and what do you think would make the most positive impact on climate change?

Green building has an enormous role to play in changing the trajectory of environmentally damaging construction practices that are so common in typical construction methods. We have gained ground in recognition of the huge role that “Building Science“can play in improving longevity/ durability, health and energy efficiency. Even so, the rate of adoption of deep green solutions is way too slow and needs to be set into wider incentivizing frameworks, like municipal level and statewide requirements similar to the Title 24 energy standards and Cal Green. Integrated transportation solutions and low carbon city planning is essential to concentrated population centers which have such enormous influence in wider society. De-carbonization of the most widely used building materials is essential. This is to a very great extent dependent on the many design professionals currently practicing. Their education in and advocacy for comprehensive ecologically appropriate solutions is crucial and needed now more than ever.

Realistically we are in trouble that is fast approaching and we need to be adaptive beyond our historical imprinting- the current weather patterns are telling. Sea level rise is accelerating from the decimation of the Greenland and Antarctic ice shelves and our timeline has become more narrow to get best practices and effective solutions more widely in place. I remain concerned for our childrens lifetimes and the generations that follow them and what they will be facing-

Sorry to close on such a dire note but it is true and should motivate us actively !