Preparing the sub floor for hemp insulation

Using some old joists from other parts of the house that were knocked down we managed to retrofit the floor so that we could create a dumping space for lovely thick hemp insulation in the old part of the house.  It has been somewhat breezy around our place with the wind whistling through the place.

We have made sure that any pipe that has hot water going through it is also well insulated.

All of this has taken months longer than anticipated, there were a number of stumps that had to be replaced, working within a tight space caused damage to Grant, in fact he broke his finger and has been working on the house one handed for months! A week later Sam damaged his thumb, thankfully he recovered from that injury, the hospital started getting suspicious.

under joists

preparing pipes with sleeves to insulate

using old lathes to sit across the under joists, then
followed by the breathable fabric, finally the hemp
is dropped in to that space

Hempcrete underfloor insulation

Had a good day of work today, managed to fill the link (hallway between the old house and the hempcrete renovation). Once it dries we can get the floorboards laid!

We are trying to recycle any products we can. These slats, originally from our lathe and plaster walls in our house have been trimmed and de-nailed to fit between the joists. The membrane (leftover from outside wall) has been laid over the lathes and then we covered it in hempcrete, same recipe as ceiling insulation (no sand and half the lime). This will provide the most amazing floor insulation.

We are a little nervous as our dog is not terribly bright and is likely to walk on the setting hempcrete insulation.

Retrofitting continued..

We are now making some good progress with the back part of our old house. The kitchen and study area have had cladding put on. This area is going to become a bathroom and laundry. The links to our other retrofitting posts are https://hempcretehome.blogspot.com.au/2016/09/retrofitting-original-house-with-hemp and https://hempcretehome.blogspot.com.au/2017/04/retrofitting-internal-walls-and-ceiling

I feel like our renovation is suffering from the 80:20 rule. 80% complete and it takes 20% of the time, 20% to go takes 80% of the time.

The left side is the laundry and the right side is the bathroom

The laundry and bathroom with the windows in and cladding on.

This is where we are going to build a bicycle shed. The wrought iron gates that can be seen were
bought second hand from Ebay,, a good way to reduce the need for buying something new.

Looking towards the back of the house. The back yard really needs an enormous amount of work.

This is looking into what used to be our dining room, it will become our study/guest room/
second living area

The same image but now hemp insulated and cladded (almost.
Another retrofit post showed the hemp.

Hempcrete performance....is it working??...bloody oath!

I took four photos today at about midday. I just thought I would check the temperature of different parts of the house....how good is this!

This is the back of the house, completely hemp built. We have 2 hydronic panels installed but have not yet
turned them on this winter. This is thermal mass and amazing insulative properties doing its thing!
However, we weren't quite brave enough to forgo heating entirely. I don't think the space would remain
warm enough if there was a week of overcast days (although that could be my next test).  Now
this is still not as good as it will be due to the link. The space between the hemp renovation
and the old house. The link is drafty with gaping holes in the floor and ceiling.

Brrrrr....This is the temperature of the drafty link, just a single sliding door away from the hemp
renovation.We are definitely keeping that sliding door shut!

This is my daughter looking stylish in front of the stated sliding door
that is keeping the chill out. As you can see she is on her way
to an 80's party with a very genuine look.
It helps when the 80's was your era
....and the era of your friends!!!

I had the heating on in the old part of the house in the morning before it turned itself off
at around 8.00am. By midday the temperature had dropped from 19C to 16.5C, a little cold
to be comfortable. This part of the house are bedrooms and are empty for most of the
day, so it is ok being this cool. Before the renovation I had to use heating if
I was working from home because 16 odd degrees and dropping is uncomfortable
and my typing fingers would get cold...oh poor me!

This is the outside temperature when I used this device (thingy)
pointed at an outside wall.

Retrofitting internal walls and ceiling

We are in the process of finishing our retrofitting of hempcrete in the back of the old house and wanted to share some tips and tricks we developed along the way.

The wall shown here is an internal wall that we are filling for thermal mass rather than insulation so we are tamping it  very firmly. The wall is only a standard 90mm thick wall, so on the hallway side, we used MgO boards as permanent formwork so that we have only a single surface to render or paint. Otherwise, we would have had a mix of hempcrete and timber substrates to render. The side shown here will be behind floor to ceiling laundry cupboards so it will have no finish or board over it.

Filling to the top of a wall that is only as wide as the top plate or any lintels is challenging as you can't fill from the top. We found that cutting a corner of the formwork to give enough access for a hand allows 2/3 of the space to be horizontally tamped. Filling the final 1/3 is tricky but as the opening is small, the hemp can be pressed in by hand and will stay in place.

We have relined the ceiling in the back of the old part of the house with MgO board. It has been finished and is insulated with over 200mm of hempcrete. The mix in the ceiling space does not include any sand so it is a much lighter and mix and is much quicker to place.  Just tip out the buckets of hempcrete and rake over the MgO boards. No tamping required.

The kitchen, dining and lounge room are finished!

The renovated area is up and running. On Christmas day we were able to accommodate 18 for lunch and then two days after that for Sam's 18th we had 26 for lunch, we all had to be inside as it was 36C outside on both days! The outside of course is still a work site so not terribly inviting! I'm really pleased with the kitchen decisions. The green marmoleum has a calming effect, it has cork underneath it to provide some cushioning while working in the kitchen. The stainless bench's provide a quiet and resilient surface, the more scratched the better it looks. The timber island bench has a very warm feel to it, it's lovely to sit around and eat casually. I've managed to sit 8 people around it when feeding the hordes. 

I used some extra venetian wax around the wet areas so that there is less chance of the lime render getting water damaged or stained, I also added extra wax at floor level (where skirting boards would normally be). I do have some vague concerns about how this will work. Time will tell. The Otsumigaki is supposed to be robust, I hope that this is the case!

Coffee and morning routine area. Looks so nice with nothing there! Doesn't look quite like that now.
We have left a display of hempcrete behind the glass splashback.

As you can see we have tilt and turn windows that provide excellent cross ventilation

We needed to add stainless steel ends to the island bench top because it was drooping a little.

The round sink is used primarily for washing fruit, and glasses of water. I would never
recommend a round sink as your primary washing up space, they look pretty, however
are terrible to use.

Still room left over in the lounge room after setting up
the double length table! Very happy.

Grant made the island bench and light above it from 2 old drafting tables he bought
20 or so years ago when he worked at Holden. He also made the top of the
entertainment unit from the same tables.