#2 Getting Started
How to get started with a passive house retrofit. Research. Your House. Budget.
Once we decided that we wanted to do an Enerphit project it was time to do some research to understand what it would involve. For us this was to answer two questions:
Would doing an Enerphit retrofit be practical for our house?
How much was it likely to cost?
Research
Fortunately my interest in Passive House meant that for me doing the research was mostly enjoyable, and I probably over did it… Anyway, it would be helpful to set some basic goals/ time limits to prevent analysis paralysis. For us, the intent of our research was to:
Get an understanding of the components (insulation, airtightness, windows, heat recovery ventilation) used in Passive House
Understand from previous Enerphit projects what type of components were installed for similar houses to ours
Be able to piece together a rough budget to know if we were being delusional
Alternatively, one could cut right back on the research and leave it all in the hands of a Passive House designer - although you’d still need to have some idea of what you wanted so that your designer had a starting point.
Resources I found useful:
Just about any of their blogs are great. I particularly took a lot from:
As the name implies, it’s a database of all Passive Houses. Filter for Australia or other similar climates to see what components, contractors and consultants were used to reach the Passive House standard.
Similarly located in Melbourne this was one of my first primers on Passive House for the Melbourne climate
Passive House Project Documentation
Again, filter by Australia or similar climate. This has much more detailed project documentation than the Passive House Database, and often includes drawings and explanations of challenges that were encountered during projects.
Projects I found useful:
About Your House
Before jumping in to the Passive House components, it is necessary to understand what you’re dealing with with your existing house. It is beneficial to know the existing structure and what, if any, aspects of the Passive House components you already have.
Note: this can initially be a bit overwhelming, particularly if you’re not experienced, up with the construction jargon, or have no idea what you’re looking at if you jump under the house or into the roof space, but stick with it and take lots of photos, you’ll figure it out!
Things that are important to know include:
What is your floor structure? Some examples include suspended timber floors or concrete slab. It’s possible you’ll have a mixture of different floor types, particularly if your house has previously had extensions.
What is your roof structure? Flat or pitched, or a bit of both? What material is it made of? Colourbond, ceramic tiles, or other?
What is your wall structure? Typically this will be one of solid brick, brick veneer, timber frame, or double brick with a cavity.
Additionally, for each of the Passive House components (remember from the first post), what does your existing house feature in each of these areas? For example,
Insulation - do you have any existing roof, floor or wall insulation? Or don’t know?
Airtightness - what forms your existing airtightness barrier? Are there noticeable gaps? Think around windows, open chimneys, and where pipes and electricity cables come into the house.
High-Performance Windows - do you have single or double-glazed windows?
Mechanical Heating Recovery Ventilation (MHRV) - it is highly unlikely you’ll have a MHRV system, but what existing heating, cooling and ventilation do you have? Hint for ventilation think of bathroom, laundry and kitchen exhaust fans, including kitchen range hoods. Also think about your hot water system.
Thermal Bridges - this is probably the hardest part to understand, basically you’re looking for uninsulated materials that are continuous between the inside and outside of your house, here are some examples:
Aluminium framed windows - metal conducts heat between inside and outside via the aluminium frame
Chimneys - bricks are great thermal mass when they’re working for you but not when they’re conducting cold into your warm house.
Steel beams - often used for structural support, but if they are in contact with outside air, and continue into your house, they are transferring heat between inside and outside.
Finding Out About Your House
All of the ‘information’ about your house can be a bit overwhelming, so how do you get all of this information? Here’s what we did:
Lodged a building plan search for our property with our local Council. For us this cost $160 but was invaluable, and captured an application that was lodged for an extension and renovation that occurred in 1980. This also had information on our floor, wall and roof structures.
Got our hands dirty - we climbed up into the ceiling and under the floor where we could, we were cautious, and wore masks - these are dusty places. We took lots of photos. If you’re unsure of what you’ve found you can show the photos to friends who are more construction savvy, or at least you can provide them to your Passive House designer who’ll know.
Looked around the house for all of the air-conditioning and hot water services, taking photos of them and their ‘nameplate’ which features their model number etc. Again if you don’t know what you’re looking at, the photos capture the information for your designer.
Felt for drafts around windows, floors, ceiling, pipe penetrations etc.
If in doubt, take a photo, show a friend or post to a renovation forum, or ask your designer (once they're engaged), and if you’re really struggling you can get a professional to come and fully document your house. Again, if you’re missing some information that’s fine, it’s just about trying to be as informed as possible.
Passive House Components and Their Suitability
With the information about your house at hand, you can go back to the Passive House resources we posted above, and see what other similar house have done to achieve the Enerphit standard. From the research we did, and with the basic understanding of our house, we came up with some rough ideas of what we would do for each component.
Insulation
Whilst there are many, many types of insulation, the main thing we wanted to figure out was where it would go. Broadly, insulation can be internal or external to your walls or in a wall cavity; on your ceiling or under your roof; and under or on top of your floor.
Starting with the walls (we have double brick with a cavity), we didn’t want to go with internal insulation as this would (essentially) involve building another wall within every room (i.e. shrinking every room) and seemed too intrusive given we weren’t planning a major renovation and didn't want to move out during the renovation. Cavity insulation didn’t seem like it would provide enough thermal resistance for Passive House (this assumption will get debunked later), so that only really left external wall insulation. External wall insulation isn't without its challenges though as we would need to relocate some downpipes, and we have water and gas pipes running along the side of the house.
Insulating the ceiling seemed fairly easy as we have good access, and also it is very commonly done (i.e. low cost).
Under floor insulation was most appealing as we didn’t want to build a floating floor over the existing polished floorboards. This also seemed achievable as we have a suspended timber floor.
Airtightness
From our reading, plastered brick walls could act as our airtightness barrier, so that was an easy win as we already had those. Although the ventilation grates in the brickwork would need to be filled.
Under the floor and along the ceiling we figured we would need to install an airtightness membrane and somehow join that to the internal plaster walls. The windows would also need to be replaced and joined to the airtightness barrier.
High-Performance Windows
Half of our windows are very old, single-glazed so they would need replacing with double or triple-glazing. There are some existing double glazed windows we were hopeful we wouldn’t have to completely replace.
Mechanical Heat Recovery Ventilation System
Yep, we would need one of them. But on the up side our reverse-cycle, ducted air-conditioning appeared to be approaching the end of its days, so the timing might work out well.
Thermal Bridges
We’ve got an old fire place and chimney that goes through the ceiling and roof line. We planned on leaving dealing with this to the designer!
Budget
Once we got an understanding of how houses similar to ours achieved the Enerphit standard and what components we thought we’d need, we put together a rough bill of materials.
For our place, it seemed like we would need:
Underfloor insulation & airtightness membrane
Ceiling insulation & airtightness membrane
External wall insulation & rendering
Double or triple glazed high performance windows.
Mechanical heat recovery ventilation system
We looked up sites like HiPages, Pricewise insulation, Logikhaus and Laros technology to get an idea of costs per square meter for different components. Combined with the dimensions of our house we could put together a rough estimate of what an Enerphit project would cost. This was to help understand whether we could do the entire project within our current budget or need to break the project into a few phases.
At this point, we were doing some pretty rough, and possibly pointless, estimating of costs, but at the time we found it comforting and it gave us some guidance.
Floor
Insulation: $12/sqm for R2.5 (maybe not enough for Enerphit), excluding install
Airtightness membrane: $7/sqm excluding install
Install cost: estimated 2 days x $100/hr
Ceiling
Insulation: $15/sqm for R6 excluding install
Airtightness membrane: $7/sqm excluding install
Install cost: estimated 3 days x $100/hr
Walls
Insulation: $50/sqm R4 external wall insulation excluding install
Install cost: 5 days x $100/hr
Rendering (required over the insulation): $80/sqm installed
Windows: $1450/sqm including install
Mechanical Heat Recovery Ventilation
Mechanical Heat Recovery Ventilation (MHRV): budget $15,000 including install
Margin, GST, Contingency
Margin: if the works are to be coordinated and managed by a builder they will add their margin
GST: make sure this is accounted for
Contingency: for when things don't go to plan. We allowed 20%.
Design Costs
The costs for architects or building designers are often set as a few percent of the total construction cost. As this wasn't a new build or a major renovation, we estimated the design costs would be a higher percentage of the construction costs. Accordingly we allowed 10% for design fees.
Other Scope
It's good to consider if other maintenance work needs to be done or you want to do other renovations at the same time as your Enerphit project. We allowed for a superficial bathroom renovation.
What did we find?
With our research completed and budget compiled, we came to the following realisations:
It seemed feasible, our house could be retrofitted without major disruption
The project would need to be split into stages to suit our finances.
Next, we put this all together into a Design Brief that we sent to a Passive House designer. More on that in the next post.
Footnote:
Sources: insulation pricing mostly from Pricewise Insulation. Airtightness membrane (Intello plus) pricing from Laros. Windows from Logikhaus plus installation.
We're expecting there'll be quite a bit of variation between our budget and reality as there is a very large labour component of the project (both design and installation) , and these projects aren't that common. We'll keep you updated as the pricing comes in.
Hi Kieran,
This is great information thank you!
Just wondering what products you are investigating for the external insulation.
Thanks
Kerrie