Insulation: keeping us cosy and cool

Eleven weeks into the build and one of the key components that will make our home a high performing energy efficient house arrived on site, and is now being incorporated into the structure.

Three trucks delivered 150 cubic metres of Pavatex, a wood fibre product that will provide two layers of insulation. Insulation is one of the five pillars of passive house building design. In winter it is our house’s fleece and in summer it’s our esky (or chilly bin if you’re Kiwi).

There’s not a lot of storage space on the postage stamp.

The passive house plan created by our passive house expert specifies the required R-value (thermal resistance) for insulation based on our house’s location and climate. We’ve chosen to achieve this R-value with two types of Pavatex wood fibre product supplied in Australia by Life Panels.
The first layer to go on is compressed wood fibre board called combi-board which is added to the external side (including roof) of the frame. It’s looking good and becoming quite a conversation starter for passers by. Not only is the product not common in Australia (as it’s from Switzerland), but it’s also not common to put this layer of insulation on a home in Australia.

Combi board on the walls
Combi board on the roof

The next layer is the bulk infill layer. This layer is similar to insulation batts used in in roofs (and increasingly so in walls in Australia), but made of a very different and much nicer material that have better thermal and structural (ie don’t sag over time) properties than standard batts.

Bulk infill ready to go

The wood fibre products report to perform very well thermally and acoustically. The builders tell us it’s easy and good to use. We’re already noticing it softening the traffic noise

Snug layer of wood fibre all around the house

Not only are the wood fibre products ticking the thermal boxes for us, we also like them because they are made using wood off cuts (reducing waste), are carbon sinks and help contribute to a healthy indoor air quality as they don’t off-gas volatile organic compounds (VOCs). Winning all round. We’re looking forward to it keeping us cosy and cool and reducing our energy costs.
Next step: Gortex wrap!

Big Mumma LVL

The top level of our house is cantilevered over the car port. It creates a good looking house! However, it means there needs to be super strong beam to hold the house up in the air without a pillar of some kind.
The architects originally specified a steel beam, but we’ve had to swap this out as steel creates a thermal bridge which is to be avoided at all costs in a passive house. See my earlier post ‘What’s a passive house?‘ for explanation of thermal bridges.
Thankfully someone in the 70’s created LVL (laminated veneer lumber), which is a high strength engineered wood product. LVL is created by gluing together (laminating) thin layers (veeners) of timber (lumber) to create a piece of timber with mega strong structural strength.

LVL layers
Layers of veneer

The grains of each piece are aligned to all run in the same direction.  LVL is as strong as solid timber, concrete or steel. It’s hard to image thin bits of timber glued together make a super timber, but  here it is signed off by the engineer and proudly holding up our house!

The big mumma piece you see in the pic is 60cm wide and 8cm thick. There’s two pieces that size next toeach other holding that corner our home up.
Being an engineered product means LVL is stronger, straighter and more uniform than solid timber, and as a composite product it’s less likely to warp or shrink. All things we like in a cantilevered structure!
It also means you can get a large super strong piece of timber product without needing a super large tree.

We love it, as it’s meant we can avoid a thermal bridge, and keep the floating look of our house.

A lot can happen in five weeks

Our builders arrived on site late March, five weeks later things seem to be moving along at quite a clip. Here is a quick summary of the last five weeks.

The builders arrived on site and marked out the excavation areas for our house in the last week of March 2020.

A few days a digger arrived and dug out some nice looking soil.

There was a little rock, but luckily not too much.

After four days there was a neat hole the shape of our house.

Getting ready for concrete slab.

We have a slab! It looked small, I wondered…what have we done?

Our quirky block has a sewer main running through it and in order to build over it we need to uncover it so as to replace it with new PVC pipe.

Once removed those manky pipes old terracotta pipes need to go to the tip for recycling.

Once replaced the new sewer pipe was encased in concrete – with a careful gap left between slab to avoid thermal bridging.

Block work getting started for the retaining.

Once we had the frames went up we had a better sense of just how compact our house will be.

Our new end of the day ritual is to pop down and check out what the builders have been up to each day.

Imperfect process

In a perfect world we would have designed our house to be a passive house from the very beginning. They are design principles after all! However, as I’m sure you know it’s not a perfect world and we were lucky enough to buy a vacant postage stamp piece of land with approved house plans. Although we weren’t involved in the original design process with the architect to create the house design we liked the plans and were happy to build it as our home.  We are very impressed with the use of space and how a three bedroom home can fit on a block of land the size of other peoples backyards!

Rather than start from scratch and create a new passive house design we are aiming to build the house as a passive house. To do this we need passive house experts on our team.

We found our passive house expert via friend after I posted on Facebook about our land purchase and passive house dreams. We are incredibly grateful to the architect who we have engaged that she is willing to take on the challenge of working out if and how we can convert someone else’s design to comply with passive house principles to achieve if not a passive house, then at least a high performing building.

Not only is our passive house expert happy to work with us on a design we inherited, she is also supportive of our plans to make a compact house a family home.

The first step was a passive house feasibility study to see if it was possible. It looked like it could work – so we kept going. It is a challenge as the small site and approved complying development certificate (CDC) leave no wiggle room to change the building envelope, we can only really play with materials and construction methods.

Our passive house expert is now doing a full modeling process for us to recommend how we avoid thermal bridges, create air tightness and insulate appropriately (all within our strict budget) to help us achieve a high performing energy efficient home. I think it’s quite a brain teaser for her and again we are grateful she accepted the challenge despite the imperfect process.

Before digging a hole – What we’ve been up to on the postage stamp

Between purchasing the land and the builder digging a hole we’ve been busy getting to know our postage stamp and tidying up in order to hand a clean site over to the builder. Between the summer heat, bushfire smoke and torrential rain we found time to:

  • prune a few trees (someone was very keen to dust of his tree loping skills and gear)
  • pull up about 950 pavers and stack them for potential reuse (although, they will probably end up at Kimbriki tip)
  • knock down a small brick retaining wall (we imagined we’d clean the bricks, I even watched YouTube videos on how to, but they’ve ended up at Kimbriki for recycling)
  • try numerous times to get Gav’s kids to help (minimal success even with offering to pay them
  • break up some concrete drains (that was a workout for Gav)
  • load 9 trailer loads of brick and concrete averaging about 800kg each (that was a workout for both of us)
  • unearth and stack a few hundred bricks from an old drain (it’s slightly more likely that we might reuse these)
  • have a competition to see who could kill grass the best (I’m still a bit dark that Gavin’s poison beat my light restriction technique). Dead grass weighs less than live grass and reduces the fee for the excavated soil removal.

We didn’t have to do this prep work,  but it saved us a few bucks in demolition fees. If we hadn’t done it we would have missed out on the fun of a trip to emergency for a palm spike to be removed from Gav’s hand, and the 20 grass ticks we each got having a beer on the grass at the end of a hard day picking up pavers.

None of this has anything to do with passive house, except maybe the need the need to save money. Nor was any of this complicated building work, and was only a tiny bit of effort and work compared to what the builders are about to do.

The weekends we were working on our block were also a really nice time to get to know many of the neighbours as they walked past on their way to the beach or shops. Seems likes we will be moving to a very friendly neighbourhood.

What’s a Passive House?

We get asked this a lot when we tell people we’re building a passive house, and that’s fair enough as it’s not yet common in Australia. Passive House is best explained by the experts which I’ll link to at the end of this post. We’ve had to create an explanation that works for us when talking to friends and family. People often think we’re talking about passive solar design, which is also an awesome set of design principles, and although it shares some similarities it’s quite different to passive house.

I normally say something like this: Passive house a set of design principles to guide creating a high performing energy efficient home. It should mean that we hardly have to use any mechanical heating and cooling to keep the house comfortable all year round (keeping energy use and bills low). The principles are based on preventing hot air coming inside the house during summer and stopping cold air coming inside during winter; this is achieved through the use appropriate insulation, super air-tightness and preventing thermal bridges. It’s very much about building a home suited to the local climate and the particular site and not specific checklist of materials and technology. We should end up with a very comfortable home in terms of temperature and a healthy home in terms of indoor air quality.

So far most of our family and friends have been both supportive and fascinated by what we want to achieve. My explanation of passive house sparks further conversation generally around the need for air-tightness in a passive house, explaining a thermal bridge, a little about insulation, windows and air quality. 

Tighty tight tight!
Passive house is a lot about air-tightness. Most regular house are not airtight – you don’t necessarily see air gaps, but they are there in spaces around windows, places were services have been brought inside from outside, where the roof meets the walls, under doors etc. All these little gaps allow hot air inside during summer and cold air in during winter. They also mean all the cool air you create with your air con slips outside and means your AC has to work harder.Many regular houses have about 15-20 air changes per house, where as a passive house aims for 0.6 (link).

How do you make it air tight?
Air tightness is achieved in a passive house by two main things:

  1. Wrapping the house in an airtight membrane that lets moisture out, but doesn’t let air through. It’s often describes as a Gortex jacket for your house. All the edges of this membrane are then taped. If you follow any passive houses on Instagram the wrapping of the building is a key and proud moment in construction.
  2. Attention to detail! The trades people on site need to be fastidious about sealing up all gaps and holes even the teeny tiny ones. Occupiers then need to be fastidious about not creating new holes as they live in the house.  Careful how you put your pictures up!

What is a thermal bridge?
As far as PassiveHouse is concerned, its a bridge too far 🙂
It is any part of the building that directly connects the outside of the building that is able to transfer heat (or cold), such as a window frame, beam, or a piece of glass, or even where services come into the house!To build a passive house all thermal bridges must either be broken or designed out.  An example from our case is the original house design had a supporting steel beam over the carport that with the engineers approval have replaced with laminated beams, usually called LVL or GluLam.Windows are also a classic thermal bridge and mean passive houses need double or triple glazed windows and thermally broken (in the case of Aluminium) or uPVC, or at the high end timber.

So, you can’t open your windows?
We get asked this a lot. It’s normally the first question after we have raved on about air-tightness. Yes, we can open the windows and we will be opening them a lot. With two kids, a dog, a love of sitting outside for beer at the end of the day and living in a beach side suburb we’re hoping for a lot of indoor-outdoor life.  Opening the doors and windows just means the house isn’t ‘performing’ as optimally as it can, but we will be as humans if we’ve got an indoor/outdoor life and a healthy home! The house will return to high performance when required.

Double glazed windows
Double glazed windows are another key component of passive houses.  In some climates triple glazed windows are needed. Regular single glazed windows are huge thermal bridges (see above) and allow heat and cold to transfer in and out of a building.  Double and triple glazed windows are incredible pieces of engineering that mean you still have a window to let in light and views without transferring heat and cold into or out of the building.Operating them can take a bit of getting used to as they open and close differently and feel very different due to that fact that they are intricate pieces of engineering. A bonus of double glazed windows in they also block out noise. Being near a busy road we hope we will enjoy this feature. There is also a benefit from a security perspective as the lock in up to 6 different points around the frame.  Bear in mind that double glazed doesn’t necessarily mean air-tight!  Trap for young players right there and we’ve needed to do our research and specify this.

Appropriate insulation is key to stopping or slowing heat (energy when it comes down to it), moving from outside or inside or vice versa depending on the season.

Fresh clear air
The air-tightness required to keep a passive house thermally comfortable could pose a problem for fresh air inside the house, if it wasn’t for a mechanical heat recovery ventilation system (MHRV). The system allows fresh air to come inside and stale air to go outside without transferring heat, nor does it let dust or pollen inside. I can’t wait! We can have the windows closed and fresh filtered air inside. I’m allergic to a lot of pollen’s – they will stay outside, but my inside air will be fresh. I hope we never have bush fires and smoke haze like we did in summer 2019/2020 ever again, nor another dust storm, but if we do, it won’t get inside our passive house.

Thermal comfort
Apparently a passive house should stay at around 22 degrees all year round without needing additional heating and cooling (link). There might be a few extreme days either hot or cold, but we hope a small split system AC unit will help us out on those days. As Gavin loves to say: A friend of mine once said of Passivehouses in Europe “Fart in Autumn and it keeps you warm until Spring”🙂 It’s not strictly true, as no system is 100% efficient, but suffice to say that the need for heating or cooling  is seriously reduced.  Typically passive houses require 10% of the energy of a Australian Building Standard house.

Further details
My explanation in this post is the over a beer intro version of what a passive house is for someone who hasn’t heard of it before. It’s the very basics, to actually design and build it requires a lot of science – modelling, research and understanding of material properties – it’s all physics. We have engaged a passive house architect to help us work out how to build our house as a passive house; more on this in future posts as the work she is putting into working out how to make sure our house is high performing is enormous and deserves a post of it’s own. In the meantime if you’re interested to know more about passive house check out the Australian Passive House Association or the International Passive House Association.

A builder, found we have

Using the Force to find a builder.

As you know finding a builder to build our passive house was a roller coaster ride. Turns out the perfect builder for us was just around the corner. Literally.
Feeling flat about all the conversations that weren’t eventuating into an arrangement for us, Gav went out for a mountain bike ride. At the end of the trail he stopped to chat to a guy who drives the same kind of electric vehicle and has an impressive solar array on his roof. Talk of EVs and solar led on to our passive house project. Gav said “I don’t suppose you know any builders?”. The guy said there was a bloke building a house around the corner who seemed good. We sent a message to the email address on the hoarding on the site around the corner. We were high-fiving each other when we received a reply that he used to build passive house in Europe and would love to get back into it here in Australia.
After the long road to finding a builder we felt like he was our only hope, so I called him our Obi-Wan Kenobi.

Not only is our builder joining us in some fun with Star Wars references, but it’s also turning into a promising collaboration. We are excited to have him and his team coming onsite soon to use the force to build our passive house.

Who knew finding a builder is like online dating?

It made us both laugh when I compared the emotions of finding a building to online dating.

You search online, shoot off an email to one or two who look good, swap a few messages back and forth about your dreams, it feels like you’re on the same page, or they at least sound pretty good so you arrange to meet up.

You meet up and chat, tell your story, share your dreams, open up about whats important to you. They say they will email you. You’re excited so you check your email constantly and then.. nothing…. you follow up…they have excuses… you believe them… then nothing. Ghosted. 
You meet up, it goes OK, they say they’ll email you.., they do, but clearly they weren’t listening. You politely decline. 
They say they will email you, you’re keen you like them, you think they get it, you get a buzz of adrenaline when their email arrives, but then as you read it, your heat sinks, they want more commitment than you can give.

And there were a few friends with benefits in the mix.

Finding the right builder is important and was another roller coaster ride for us. It’s our home and our entire savings so it can feel emotional. We did often feel hopeful as we went to meet a new builder on site wondering if they would be the one. We also often had our fingers crossed waiting for their proposal to arrive hoping it would work for us. 

I won’t go into the details of builders that didn’t call us back, builders that seemingly didn’t hear our budget, those that said they’d be in contact and then we never heard from them. We presented honestly, friendly and passionate but professionally each time. If they had too much on, thought we were dreaming or weren’t interested in passive house, that’s OK – just let us know.

We also met some wonderful builders and other building professionals along the way who even though they couldn’t deliver the whole project were very generous with their time and advice. We are super grateful to these and hope to stay in touch.

Some people wonder if we complicated things by wanted to build passive house, but we wouldn’t have been true to ourselves and our values if we had built the ‘conventional’ way, so I can’t answer that.

In the end we’ve found our perfect builder, which is another serendipitous story, for the next post.

The postage stamp

You bought what? How did you find vacant land on the Northern Beaches?

Gav has been talking about wanting to build a passive house ever since our first date. How and where to find land on which to build occasionally came up, but I didn’t hold out much hope of finding something locally, especially after Gav showed me the only block of vacant land he’d seen that had been on the market for ages. It was way up the peninsula and had an inclinator! I said no to that one, and realised that there aren’t many options for vacant land around here. I also (half jokingly) said I didn’t want to go further North of Manly than Freshwater! The journey to purchasing the block we are now building on was a roller coaster ride, but has some nice moments of serendipity.  For the first few months of the conversation about building a passive house we weren’t in a financial position to do much about purchasing land anyway, so it was something Gav mostly chatted and dreamed about.
A few months later Gav knew he would soon be in a position to buy something. Wanting to get his head around what the market was doing Gav met up with a real estate agent he’d worked with previously for a coffee. At the end of the conversation he said “If I had a magic wand I could wave I’d ask for 200sqm of land on the Northern Beaches where I can build something clever”.  Two days later Gav is updating me on his conversation and his closing wish. Next thing I know he’s opening up the laptop saying “I’m just going to have a quick look, and see what’s out there”. We were slightly incredulous when the first thing in the search list was 200sqm of land in Freshwater listed only 4 hours earlier! The sale of land included approved plans for an architecturally designed house and was scheduled for auction in 5 weeks.  We swung by the next day to have a look and then jumped into action contacting the agent, applying for a loan and pouring over the house plans. 

What to offer?
200sqm is tiny. It’s smaller than some people’s back yard and vacant lots are rare – so we had no idea what to offer. None. We pulled numbers out of the air and tried to imagine if the block was worth it.Whilst discussing the opportunity and conundrum with friends over dinner. Gav flippantly said “I don’t suppose you know any land valuers?” It tuned out my friend did and offered to ask them to take a look. The next few days were busy with getting loan approved and wondering what to offer trying to contact agent and waiting to hear from our friend’s contact on a land value. It felt like quite a hectic time as there was another party interested and making an offer. Phone calls to and fro – we offered to match their offer plus the 20k extra the vendor apparently asked for. We were literally making the offer at the same time the text from my friend arrived with their estimate of the value.  The estimate and and our offer were way more than I’d ever imagined 200 sqm of land could cost. I was only able to sleep that night knowing that our offer was in line with the valuation our friend has sourced.

Off and back on
On the Friday before the October long weekend Gav called me to tell me another offer had been accepted 😞 and we were out of the picture. 
Gav checked the ad on the website *quite a few* times over the long weekend – waiting for an ‘under offer’ or ‘sold’ notice to go up. By Tuesday morning with nothing added to the website Gav texted the agent to see if it had sold. The agent called pretty much straight away to say it hadn’t gone through. We were back on – re stated our offer and then had to contact the bank etc to make it all happen. 

Good or bad timing?
Amongst all of this Gav’s best friend was in palliative care and we knew there wasn’t long to go.  I was worried Gav wasn’t thinking straight in amongst the grief, he assured me he was. The agent took our offer to the vendor while Gav was the MC at his best friends funeral. After the service Gav took a call from the agent that our offer had been accepted. Some very happy news on very a sad day. We now owned 200 sqm of land right where we wanted – ready to build a clever home on 🙂 Although we actually ‘found’ the block on the usual real estate website – it felt like there were various serendipitous events that helped get us to where we wanted to be. Not least wondering if Gav’s best friend pulled some strings for us from beyond to help Gav realise a dream.