Episode 15. Heritage Renovations: Five Upgrades for High Performance & Thermal Comfort

Walk into almost any unrenovated Melbourne heritage home on a winter's day and the problem announces itself before you've taken your coat off. Beautiful from the street. Fifteen degrees inside when it's 22 outside.

In this episode, builder Simon Clark answers one of the most common questions he hears from Melbourne homeowners: can you really have the soul of a heritage home and the thermal comfort of a modern one? After nearly 50 heritage renovations, his answer is an emphatic yes.

Simon opens with the building science behind why heritage homes fail. Double brick walls may be less leaky than weatherboard, but without insulation they push the dew point onto internal surfaces, breeding mould. Single-glazed windows offer virtually no thermal barrier. Dark interiors were never designed with passive solar in mind. The charm is real. So is the discomfort, and the health risk.

He then walks through five building fabric upgrades SHM applies to heritage renovations: addressing compromised footings using resin injection and board piers, replacing lightweight subfloors with an insulated infill slab and low carbon concrete to create genuine thermal mass, installing Coolfirm K17 insulation-backed plasterboard internally on double brick walls using the dop and dab method, rebuilding roofs with OSB, vapour-permeable membranes, and ventilated counter battens to allow moisture to disperse rather than condensate, and restoring or upgrading heritage windows, including vacuum insulated glass units for lead light windows council will not permit to be replaced.

Each upgrade is designed to work within heritage overlay constraints, keeping council happy while transforming the building from the inside out.

You'll learn:

• Why double brick heritage homes often develop mould problems, and the building science behind it
• The infill slab method SHM uses to eliminate subfloor moisture and create thermal mass with low carbon concrete
• How Coolfirm K17 insulation-backed plasterboard transforms double brick wall performance without touching the exterior
• Why vapour-permeable membranes and ventilated roof battens outperform traditional roof blankets
• How to upgrade lead light and heritage-listed windows without breaching council requirements
• How to genuinely improve thermal comfort and longevity while working within heritage overlay constraints

Who it's for: Owners of Melbourne heritage homes planning a renovation or extension, architects and designers working within heritage overlays, and anyone who has wondered whether you really have to choose between character and comfort.

If you'd like to know more, please reach out to Sustainable Homes Melbourne or call us on 1800 683 697.

Transcript

SPEAKER_00 0:05

If you're planning to build or renovate and want a home that's sustainable, smart, and built with care, you're in the right place. This is House of Meaning by the designers and builders at Sustainable Homes Melbourne. And I'm your host, Simon Clark, director, builder with a passion for meaningful design. Since 2014, SHM has had its boots on the ground designing and building sustainable, energy efficient homes that stand the test of time. In each episode, we'll share design insights, practical advice, and real stories to help you plan your dream sustainable home. I remember one of our first major design and build projects with Sustainable Homes Melbourne. It was circa 2020, 2019 perhaps. It was a grand old girl sitting on half an acre in Hawthorne, built circa 1900 and had north to the rear and had enormous potential for an incredible renovation. I remember it was an early spring day where I walked up to the property admiring the red brick, the fretwork, and the beautiful lead light windows. And then entering the home, I was struck by these really deep brown panels that lined the interior of the entryway. And it was incredibly dark. All the lights were turned on in the entryway. I was really, you know, a two to three meter wide entry. And there was a wall in front of me that was also lined with panels, the dark brown timber panels, and that wall was basically blocking what have otherwise been the northern aspect of the home. So the client at the time led me to the kitchen on the north side of the home that had one small little window letting a little bit of northern sun in, but it was nowhere near enough not to have the lights on, or nowhere near enough to heat the home or attain any heat within the home. It was about 22 degrees outside and about 15 degrees in that double brick home, and I was regretting leaving my jumper in the car. Now I think this is a common story of some of the beautiful old heritage homes within Melbourne. You know, they're beautiful, charming, incredibly desirable architecture, but they leave a lot wanting to the actual livability within the home. So I want to ask the question today can you combine our beautiful heritage architecture with high performance? Can you have both? And I'm here to answer that. The answer is yes. So many of our clients at SHM they want the beautiful heritage that belongs so strongly to Melbourne and also with thermal comfort that is not so common in Melbourne. Of course, many of our clients want the soul of a beautiful heritage home, or combining that with the thermal comfort of modern, I'll say European homes. I don't think Australia's quite there yet with our minimum standard, even at seven stars. So I want to talk you through today of the experiences that we've had renovating many, many heritage homes. We've been renovating these sorts of homes since before 2014 when Sustainable Homes started. I was started as a builder in 2009, even previous to that, all through my apprenticeship even, so back to what 2002, I was renovating these heritage homes that sit so proudly in Melbourne. But the problem that lies within the beautiful heritage architecture of Melbourne is they are incredibly drafty and leaky. We all know that. If you've ever lived through a Melbourne winter, you know that these homes are just incredibly drafty and leaky. And if they aren't drafty and leaky, they're just super cold because they have no insulation. The double brick homes that lie within this heritage context, most of them are double brick homes. They're not so leaky, although you do get a lot of leakage through the floorboards and depending on the type of ceiling lining that you have and cracks within. But the issue really with double brick homes of this heritage nature are that they have no insulation. We had a home recently that we we blow it all tested before we commenced any work, and the result was pretty surprising. It was only seven air changes per hour. Now that's a pretty good rating. The NCC National Construction Code expects homes built today to be under 10. So seven's pretty surprising for this home built you know in the early 20th century. The problem here was that this home, well, being double brick, it's not vapor permeable and had no insulation. So the clients, the occupants, our clients, are heating the home inside, and then we're getting the dew point being on the internal of the home. That gets a bit nerdy, but ultimately what that means is you're getting condensation on the internal of your wall. And that was growing mold, and there was mold all throughout this home, and it clearly horribly, horribly bad for your health. So that is the real problem about these heritage homes, especially if they're not the leaky hollow wall weatherboard homes. Yeah, the double brick that aren't leaky at all. There's not enough air movement. We're heating the home from within, and that dew point's on the inside of your wall, and you're getting condensation there, and hence mold. Incredibly bad issue. Of course, these homes are dark, as beautiful as they are, they were never designed to be passive solar, they were never designed to consider where the sun might be. Potentially, there were many English and European architects that were designing for the northern hemisphere thinking the sun was on the south. I don't know. But very few of the, if any, of these homes are designed to open up to the north, to allow the north sun in, keep it out in summer. And of course, windows that are leaky. They're typically single glazed, four mil, very, very thin glass that may as well have have nothing there. You may as well have glad wrap there because they don't keep any cool or heat out. It just lets it straight through. And there's many conflicts here, especially when we've got heritage homes. Of course, the biggest one being heritage preservation. It's a huge one. Of course, cost can be another one for some people. And then there's just the sensitivities to can you reproduce an element of the home that celebrates what the home once was and the heritage aspect, the heritage charm. So having completed nearly 50 of these heritage type renovations and extensions, I want to talk you through. I've got five things that we use, really focused on the building fabric of the home. It's you know, that's what separates us inside the home to outside. Anything you want to apply inside, great. Anything you want to apply outside, well, you better check the council first. But I want to really focus on how you can improve that existing building fabric, of course, keeping thermal performance in mind, keeping council happy, and of course, longevity for the occupants and the family that will live in the home for many, many decades. So, number one, simple with any renovation at all, deal with the compromised footings. I know this isn't a such a thermal comfort type of thing, but you don't want to go and spend a couple million or a million dollars on a heritage restoration and still leave compromised footings. Now, of course, many heritage lists homes will have bluestone footings. Now there's great issues with bluestone footings generally. Well, actually, I'll take that back. There's issues when trying to rectify them. The only real way that we've found, we've very rarely uh had any hands-on experience dealing with the shale type of heritage footings, actually re-inforcing them because we found that they've lasted 150 years, there's not been any cracks, let's deal with it. Let's leave it. But of course, if there are cracks, often you demolish and start again. Honestly, even if it is heritage, of course, you've got to build it again within heritage constraints and council would be all over that. But if you are to try and improve the integrity of heritage footings that are bluestone, because it's not all tied together, it's not all one sequence of footing that's tied together. Resin injections are likely your best choice. Of course, if for more modern footing systems where you've got concrete beam in the ground, we've had cases where the previous renovation or previous extension had caused the footing to drop 90 mil over, it was about 14 meters. We actually were able to dig under that spot dig, use jacks to jack that up back to level, you know, so the whole thing moved as one, able to jack that up and re-pour no shrink grout and improve that footing to level, which was fantastic result. And that had bricks in on top of it. We've got a great result there. But when you're dealing with bluestone footings, it can get a little tricky. But a lot of these footings have lasted 150 years and are in pretty good condition. So I'd say if you can leave it, leave it. Of course, when when you're building new structure around it, you have to be very careful, get engineers' advice. We often like to, again, that spot sort of dig method using board piers, we're not undermining that existing footing. That's another topic. Go into another time. Sticking with the footings, number two, or the footing or the base area. Number two is we've been installing, especially around double brick, we've been installing an infill slab opposed to lightweight timber subfloor, especially for double brick homes. Now, this works incredibly well. It means we don't have ventilation issues, we don't have moisture issues with getting under the property. What it means is that we're able to lay insulation. What it means is we've got our brick walls on either side, all around, four sides, of course, keeping the front two or three or four rooms, plus the hallway. We're able to lay insulation all the way around where we're gonna pour that slab. Then, of course, our vapor barrier, and then we simply pour low carbon concrete. It's easy, it has been the simplest solution we've found. You don't have to deal with any ventilation, don't have to deal with any rising damp. It's just done, and you've got a completely insulated layer. And that's and the ultimate is that we've got insulation on the external with this. Is the same principle for walls, of course, for floors as well. So we've got insulation on the lower layer between the earth and our slab, and then and we call the slab thermal mass. It works incredibly well. We're wrapped with this finding, and it's much more cost effective. Everybody's winning. And now internal insulation. Now I'm very much focused on double brick heritage homes here. Of course, you've got lightweight heritage home, you can of course put insulation within the wall. But for double brick, especially with heritage listed, you've only really got one choice, and that's internal because heritage don't want you affecting the exterior of the home. So, what we used to do years ago is put internal battons on the internal of the brick wall, and then insulation in between, run all our cabling, of course, and insulation in between, and then just plaster over that. Now there's a new, well, it's not that new anymore, but there's a product, it's called Cool Therm K17. It's insulation backed plaster board. We like to use the 60mm thick layer, and that gives us an R2.35. We only apply that to our external brick walls, and voila, we've turned that double brick wall that was incredibly cold in in winter. We've turned that into a wall that is comparable, basically matches what the standard Australian wall buildup is for insulation value, all in one product being that plaster board. Of course, the plaster board is more expensive than just a plaster board because you've got insulation with it, but it's incredible, it works incredibly well. Use the dop and dab method if you're familiar with that from the UK or in Europe, be very, very common. No mechanical fixings, away we go. And of course, that combined with our slab insulation, which is also 50 mil. Now we've got our 50 mil under our subfloor, it just edges up the wall as well to the top of our slab, being 150 mil thick, whatever that is, often might be 300 in some of these homes. And then our K17 basically connects to that about 10 mil gap we have, and we just cork that the appropriate spray foam. So we've now we're now we're getting toward a completely encased insulation layer. And number four is updating the roof structure. Now I'm not going to talk about insulation here because just to clarify, that insulation that runs under your subfloor, up your wall, should also run through your ceiling. But when we're talking about the roof, of course, we're talking about the layer above your ceiling, often on the pitch with these heritage homes. And now, what we do there, what we've done recently, many of these heritage homes, of course, are roof tiles. And so heritage won't want, don't really want us changing that to a corrugated roof. Of course, corrugated roof, the same principle really applies. But in a recent case, we had in Carlton, Carlton North, is we had a roof that was tile, ceramic tiles, it was leaky. We had to address it. The issue, I suppose, with addressing these old roofs is that they don't meet the current construction code for gutters. And this one has parapet wall on each side, and therefore it's got box gutters. And box gutters is very critical. I think most people that have built a home has heard horror stories about box gutters. Box gutters done right, should work, and I think the code has probably changed to upgrade them, gone over the top, I think, but certainly should deal with any potential leak issues from a box gutter. Anyway, in this case, we had to address the box gutters as well to make them meet code. So all the roof tiles have to come off, we had to rebuild sections of the roof, add it's called a layer of OSB, about 16 mil or 12mm. I can't exactly recall, but basically like a ply, but it is vapor permeable. So we lay that over the rafters and then we put our counter battens on. Let me go back. So we've got our OSB, it's basically like a ply that sits on top of our rafters and our new box gutter. And then we put our vapor permeable membrane down. So in this case, we don't apply an anticon, anticondensation wall roof blanket. Many people, especially roof plumbers, would advise to do a roof blanket. Go on to those days, I believe, because we want our roof to be breathable so that vapor disperses through, where roof blankets they're not. So this avoids the potential condensation layers that a roof blanket can have. So we've got our vapor permeable membrane on top of our OSB, similar to ply, and we lay our counter battens on. Our counter battens ultimately are acting as our air gap, and then we put our battens on to pick up our tiles in this case, be the same principle for roof sheets as well. So ultimately, what we've got, and then of course, on top of that is our tiles or our roof sheets, and then what we've got is basically a 20 mil layer that sits underneath those tiles, continuous layer that allows ventilation through. So we're expecting in these homes, in a modern home that's really well insulated, vapor to come up through the ceiling. Plaster board is vapor permeable, it'll come through your insulation layer in your ceiling, and it'll hit the bottom of your roof, and then it'll also vapor diffuse through your roof, and then it'll have that 20mm layer that'll be able to run down into your gutter. Now, of course, we want that vapor permeable membrane to either run into our gutter or onto the outside of our brick wall. You don't really want it running on the outside of your brick wall, but you definitely want it external. It should be dealt with appropriately with the right designer and the right builder that knows what they're doing. And then, of course, we've got window restoration. Many of these heritage homes have heritage listed windows, and they're beautiful windows. And council quite sensitive to anything happening with these windows, and in many cases, they don't even want you to change the windows, which can be frustrating. So there's a few options here. Of course, we've engaged specialists to restore these windows. That can come with challenges to when we're restoring, of course, we're upgrading those glazing units to be double glazing, which often means we need to machine the existing glazing unit to allow for a larger glazing unit, which can be challenging, basically laborious and can be costly. Depending on the value of the window, the sensitivity of the heritage nature of the window, you can often be better placed to restore, or sorry, to replace that window completely. The judgment call to make specific to your exact situation. I do want to mention here that of course, lead light windows, they're a window that's you typically wouldn't replace. So there are cases where we would install a double glaze unit, typically a vacuum insulated glass unit, which is a new sort of technology, I guess. It's a very small double glaze unit that typically rates quite well. And we would install that externally or internally at times, and of course, that increases the value and the rating of that window greatly, and of course, helps with retaining the inside temperature in and the outside temperature out. So it's no secret that our heritage architecture in Australian cities like Melbourne is precious, gorgeous, and charming to admire. In my humble opinion, the best homes and certainly the most unique homes are the ones that blend the restoration of a heritage charm with the modern day comforts a family needs to live a healthy, joyful, and comfortable life. Heritage architecture really does give a home its soul and combined with these modern day methods that I've just gone through, can really enable you to create a healthy, energy efficient, and comfortable home for many generations to enjoy. I really love the thought that these heritage homes will be preserved and hopefully appreciated long into the future by the families that live in them and of course our peers and of course builders and architects of the next generation. Thanks for listening. Until next time. Thanks for listening to House of Meaning by Sustainable Homes Melbourne. If you're planning to build or renovate and want a home that's sustainable, smart, and built with care, we hope this episode has brought you one step closer. If you enjoyed listening, be sure to like, subscribe, and share this episode with someone planning to build their forever home. Follow us on Instagram, Facebook, and YouTube or visit sustainable homesmelbour.com.au to learn more. If you're considering your own project, we offer a limited number of short introductory consultations for homeowners just like you. To request a call back, visit sustainablehomesmelbourne.com.au or email us at hello at sustainablehomesmelbourne.com.au with a few details about your project. We'll then guide you through the next steps and see if we can help. Remember, behind every great sustainable home is someone who cared.