Hempcrete for Brooklyn Brownstone Extensions

We at Eco Brooklyn have been in love with Hempcrete – a mix of lime and hemp for walls – for years. A hempcrete wall provides strength, protection and insulation all in one.

Compared to stick and frame building it uses much less wood and is much more solid of a structure. A hempcrete home feels solid. And the soundproofing qualities are amazing.

The one drawback is that you do need a thicker wall – at least 12′. In space starved NYC this can be a problem. The wall doesn’t, however need any kind of finishing (sheet rock for example) so space is saved there.

We think a Hempcrete application is perfect for a brownstone extension. It is so much greener than the cinder blocks often used. And in terms of comfort it is unmatched. No air leaks or thermal bridges.

Eco Brooklyn is a New York Hempcrete installer. We feel that it has it’s place in the NY green building lexicon. More and more, though, the green building lexicon is simply becoming building lexicon. Green building makes sense.

We are eager to install more hempcrete walls. Even if it is just one wall that acts as a centerpiece, the visual beauty and tactile comfort of hempcrete is makes it practically a work of art. Optionally you can plaster the wall with clay, another beautiful material.

Check out this video on how a hempcrete wall is built. You will notice how very simple it is.

Eco Brooklyn’s Clay Wall Application

Eco Brooklyn’s Gennaro Brooks-Church discusses our clay wall application. Creating a better seal on bricks and more insulation, Eco Brooklyn applies clay to walls all over New York City. Most recently we applied clay in our Harlem Passive House and in the downstairs apartment in our Brooklyn Show House.

Check out this great video!

Clay Wall Application

As a New York contractor we are constantly trying to incorporate the best green building techniques to New York and Brooklyn brownstones. The creative use of clay is one of our tools. We just did a another clay wall job in Brooklyn.

We switched the mix up a little to make it a little smoother, less mold receptive and possibly healthier.

Our mix was:
calcium carbonate
white sand
saw dust
clay
wood glue

We omitted two key things: silica dust and wheat paste.

The wood glue replaces the wheat paste. We did this because we found the organic nature of the wheat paste lent itself to mold. The slightest amount of water and you have a wonderful colony of mold growing up the wall.

We took out the silica because of concerns over the possible health issues. Silica is naturally found in sand but pure silica increases the amount drastically. Our concern is that the very slight dusting off the walls could cause unknown health issues years down the road for the tenants.

This may be completely unnecessary and unfounded, and in fact most clay wall mixes suggest silica, but we found we could make a good mix without it so why not? Silicosis is not a pleasant illness.

Other mixes we have had success with are:

clay
silica
white sand
marble dust
fine sand
linseed oil
wheat paste

This one gives a very smooth white finish that you can trowel down so it looks almost like Venetian plaster but still has the benefits of clay. Unlike clay, Venetian plaster goes through a chemical process and is inert. Clay does not and stays “alive” as it interacts with the humidity of the room.

Another mix we use:
clay
calcium carbonate
silica
marble dust
saw dust

The calcium carbonate makes the mix even smoother. You then add saw dust to give a contrasting texture and to add strength to the mix. Typically straw is used but we use what is local and we have lots of saw dust!

There is no right way of doing it as long as it lasts. We sometimes add milk paint either as a binder or for color. White milk paint really lightens up the mix. Milk paint comes in all sorts of great colors that really make the clay pop.

In the most recent mix mentioned at the beginning of the post we applied the clay over a scratch coat of cement that we applied to add strength to the load baring wall. If the wall is brick and you don’t need extra strength you can add it thick over the brick. This is great because you really get a lot of clay in the room. In this case the scratch coat was smooth so we added a thinner layer.

We didn’t add any color so it is the natural beige of the clay. Clay comes in a range of tones from white/gray to dark brown. We tend to go with a light sand color:

P1100687.JPG

We chose to create a smooth surface and troweled the clay once it had dried a bit:

P1100689.JPG

P1100692.JPG

Another experiment we did that worked great was pointing of a brick wall. The interior wall was in need of clean up but we wanted to keep it exposed.  So instead of pointing it with mortar we used clay. Clay offers no structural strength to the wall but the the brick was in good enough shape that it didn’t matter.

By pointing with clay we had the advantage of using clay, which has humidity control and possibly even emotional benefits to the inhabitants, and we were still able to leave the bricks exposed.

Here we are pointing the brick wall with clay:

P1100736.JPG

We’ll probably not seal the brick wall, instead we’ll just leave it bare to maximize it’s humidity control function. If you seal a clay wall you reduce it’s benefits drastically.

P1100739.JPG

 

Recycling Salvaged Cement Reduces our Carbon Footprint

Construction is conventionally a carbon-intensive industry – especially in a place like Brooklyn where most homes, coffee shops, book stores and restaurants are built primarily with concrete, mortar, brick and stone. Some degree of greenhouse gas emission is inherent in the production of all construction materials, but none more so than the cement which makes up our foundations and holds our brownstones together. After energy generation, the cement industry is the 2nd-largest CO2 emitting industry in the United States and the world – responsible for about 5% of all man-made carbon dioxide emissions.

Cement manufacturing entails a chemical process known as calcination in which limestone (i.e. calcium carbonate, CaCO3) is heated with small quantities of other materials, namely clay, in a kiln to 1450° C; this process liberates a molecule of CO2from the calcium carbonate to form calcium oxide (CaO). The clinker – which is the resulting hard end product of calcium dioxide – is then ground up with gypsum into powder form to produce what is commonly known as “Portland cement”.

From start to finish, roughly 0.9 kilograms of carbon dioxide is produced for every 1 kilogram of cement that is produced – 50% from the end-products of the chemical process itself and 40% from the burning of fuel to heat the limestone to such a scorching temperature, the rest mostly in transportation and administration. More than 70% of all energy consumed by cement kilns is generated by burning coal – the worst of all fossil fuels in terms of greenhouse gas production, about 12% from petroleum coke, 9% from waste fuels, 4% from natural gas and the rest from oil and coke.

Industry leaders and environmental scientists are trying to devise ways of reducing the environmental impact of cement production. The Environmental Protection Agency, for one, is trying to prod the U.S. cement industry to substitute coal-powered kilns to kilns which run on any fuel other than coal, CO2 capture and sequestration, alternative processes of concocting calcium oxide, etc. The state of California’s recently-enacted carbon emissions standards are forcing their large cement industry to invest in cleaner, less carbon-intensive production methods. We support these regulatory efforts, but we also believe that New York’s green contractors can do much more than to sit back and wait for change to come from the top down.

Here at Eco Brooklyn we have devised an even more effective and remarkably simple means of reducing the carbon footprint of our construction and renovation projects: conservation. Such a large amount of the cement produced in U.S. factories for some reason or another is never actually used to mix the mortar or cement it was intended for. Either contractors estimated too high when they made their bulk purchases and are left with excess cement that they don’t need, or somewhere in transit from the factory to the individual vendor cement bags are ripped or broken and cannot be sold. This surplus is considered trash on the free market – very few contractors make the effort to buy second-hand cement, so every year they take untold tons of perfectly good cement and just throw it in the landfill. From our perspective, this is throwing the baby out with the bathwater!

If there is any way that NY green builders can cut down on the carbon footprint of construction/renovation jobs, it is by reducing this wholly unnecessary waste of cement; for every 1,000 kg of cement that is thrown out, our air and our oceans are polluted with 900 kg of CO2 for no reason at all!

As a green contractor, Eco Brooklyn salvages this otherwise landfill-bound cement from conventional contractors who have overstock and merchants who are stuck with unsellable bags – not only are we reducing the volume of waste sent to our already-overcrowded landfills, but we are using it to make the homes and businesses of the 21st century.

We do procure some of our cement by conventional means, but we salvage as much as possible via conservation. By recycling salvaged cement, Eco Brooklyn is busy conducting construction projects without there needing to be any additional cement produced, energy consumed and greenhouse gases emitted into the atmosphere. By adhering to our environmentalist mission by this and other practical methods, this green contractor is committed to limiting our carbon footprint to an absolute minimum. And that is not the only benefit of salvaging cement and material conservation; Eco Brooklyn’s procurement methods are also crafted to reduce unnecessary costs from our overall production process, to reduce the burden on our city’s public sanitation infrastructure, to curb the volume of waste sent to our landfills, to do a favor to other businesses in the neighborhood and to invest in the health of our community.

Moreover, this NY green contractor is also developing new methods of building and renovation which can cut cement out of the production process as much as possible. Instead of basic concrete which is usually used for foundations, basement walls and floors, Eco Brooklyn is perfecting a rammed earth technology which simply uses the earth and stones dug up from the ground mixed with the most durable and sustainable ratio of cement and water. And instead of pouring plain old concrete for the front walkway and steps, we are using natural stones, scrap bluestone and tile. We don’t need to invest in the costliest and most exotic foreign technologies – in order to turn every brownstone into a greenstone all we can procure most of our materials straight from our own backyards – literally!

Clay Plaster Walls For New York Passive House

We are building a Passive House in a Manhattan brownstone. Instead of using more synthetic materials to air seal the brick walls (crucial for PH) we are using clay.

Here are some notes to a successful clay application over New York brownstone brick walls:

– Use reinforcment mesh (fiberglass is best, hemp is  mesh also usable, easy to work with if soaked in starch – more ridgid) wherever you have different materials that meet. On a flat brick wall, that is not moving, no mesh is necessary. but better save than sorry?! so use mesh anyways
– With clay, always make experimental surfaces and wait until dry (you can dry it with a heater, not necessary to wait for natural drying) Some surfaces (concrete, OSB) need a clay slick before applying regular clay plaster. The rule is more clay for the first layer, less clay for the next, least clay for the last. Never the other way round. Using mesh, maybe we can suffice with 2 layers? Let’s think about that.
– The first layer might crack, but that is normal and makes the second layer stick better. The last layer should be done in the same thickness and rather thin (3-4mm) over the whole surface, to prevent cracking
– You will get cracks between the plaster and for example wooden elements (ceiling or whatever). These cracks can be filled in later (just make them wet and add some clay), but any movement later will cause a minor hairline crack. If you have some hemp textile soaked in clay slick, press it to the wood with a small baton, then plaster over the whole. The soaked hemp is air tight, and any crack does not matter. Instead of clamping the clay hemp textile with wood the joist (cumbersome), we can drape the soaked cloth around the joist and then tape the edge of wood/hemp with 3m tape around the joist.

– Use reinforcment mesh in areas where possible settling or movement will occur. Fiberglass is great but has high embodied energy. Hemp works well too.  If you soak it in starch it is easy to work with and dries harder.  Wherever you have different materials that meet you especially need to put mesh. On a flat brick wall where you don’t anticipate moving no mesh is necessary.

– With clay always make experimental surfaces and wait until dry (you can dry it with a heater, not necessary to wait for natural drying) Some surfaces (concrete, OSB) need a clay slick before applying regular clay plaster.

– The rule is more clay for the first layer, less clay for the next, least clay for the last. Never the other way round. If you are ok with a rougher look or you are really good you can get away with two layers. We have even gotten away with just one!

– The first layer might crack, but that is normal and makes the second layer stick better. The last layer should be done in the same thickness and rather thin (1/16″) over the whole surface to prevent cracking.

– You will get cracks between the plaster and for example wooden elements (ceiling or whatever). These cracks can be filled in later (just make them wet and add some clay), but any movement later will cause a minor hairline crack. If you have some hemp textile soaked in clay slick, press it to the wood with a small baton, then plaster over the whole thing. The soaked hemp is air tight, and any crack does not matter.

American Clay


American Clay is a great company that is reviving a millenia old building technique of applying clay to building walls.

They have a strong local culture and associate themselves strongly with their Santa Fe roots. But to grow as a company they also ship anywhere.

They are very helpful with advice too. Shaylor at American Clay knows a lot and is genuinely there to help.

Clay is a great wall application with all sorts of benefits. For example it is one of the ingredients in backerboard that is used in wet areas like bathrooms. Clay is a natural sealant because the molecules expand when wet and seal themselves. Then when they dry they breathe again.

In terms of clay applications American Clay are the best on the market bar none. But that also has its disadvantages because clay is still in the boutique realm of green building. And that includes the prices.

$50 for a small sack of dirt is expensive. And trucking it all the way from New Mexico is a little silly.

I’m looking into local sources of raw clay to mix myself. After all, the local hardware store has ten brands of concrete mix. It is not rocket science to mix a couple ingredients together. In fact the ratios of how to mix a good clay application should be common knowledge just like concrete mixing ratios are today.

Shaylor says that Ohio has a good kind of clay and I’m looking into that. But I also know NY has a lot of clay. I’ll be doing a test so keep a look out for that. Having clay in the Brooklyn Green Show house is a must. I’d really like if I could find a local raw source for clay and get a good mix going.

For those of us who like to bring back the crafts to building that is the way to go. Build It Forward baby!

Of course if you want it off the shelf in New York you can buy American Clay at Bettencourt Green Building Supplies. Ask for Michael. He knows a lot about the clay and how to apply it. It does take a little getting used to in the application but it is easy if you know how to stucco or work with plaster.