Hemp Homes and Energy Ratings: Gary’s Advice for First-Time Builders

Building your first home with hempcrete is an exciting venture – imagine crafting walls out of a natural, carbon-negative material that keeps your home comfortable year-round. But where should a beginner start? We spoke with Gary Rogers, a veteran hemp builder in Australia (owner of Hemp Homes Australia), to get his top tips for first-time hemp home builders. From smart design choices to demystifying energy ratings, Gary’s advice will help you understand how to make the most of hempcrete’s unique benefits. In this post, we’ll share his insights on keeping your build simple, focusing on the thermal envelope, and why hemp homes excel in comfort even if their R-values or NatHERS star ratings look a little different from conventional homes.

Keep It Simple: Design with Your Budget and Hemp in Mind

One of Gary’s first pieces of advice is to keep your design simple – especially when it comes to the shape and layout of your home. “Keep it simple. Corners cost money,” Gary says, emphasizing that elaborate floor plans with numerous corners or complex angles will drive up costs and complicate the building process. Hempcrete construction is generally straightforward, but every extra corner means extra formwork, labor, and materials. For a first-time builder, sticking to a relatively simple layout (think open floor plans and fewer nooks) can make the project more cost-effective and manageable.

Simplicity doesn’t just save money – it also aligns with hempcrete’s strengths. A simpler design often means it’s easier to insulate and seal, which is crucial for any energy-efficient home. Rather than aiming for intricate architecture on your first build, Gary suggests focusing on getting the fundamentals right. You can always add unique aesthetic touches later, but you can’t retrofit poor planning. In Gary’s words, put your effort into the basics first: “If you want a hempcrete home, basically you concentrate on your outer perimeter of your home... you can do your aesthetics after that.” In short, prioritize a straightforward, solid design; it will pay off in both construction ease and the performance of your hemp home.

Focus on the Thermal Envelope (Your Outer Perimeter)

When building with hempcrete, your home’s outer shell – the walls (and roof, if applicable) that separate indoors from outdoors – is everything. “The whole reason you’re building a hempcrete home is for your thermals,” Gary explains. Hempcrete’s magic lies in its ability to create a comfortable indoor climate, so you’ll want to prioritize sealing the entire perimeter of your home with hempcrete. This means ensuring all external walls are built with hempcrete and are properly packed and rendered so there are no gaps in your insulation layer. “I’d be concentrating on... sealing your whole perimeter of your home, then you’ve got a hemp house,” Gary says. In other words, once you’ve wrapped your home in a continuous layer of hempcrete, you’ve achieved the core of what makes a true hemp home – an airtight but breathable thermal envelope.

Focusing on the thermal envelope might mean allocating more of your budget to the walls and less to non-essential extras at first. And that’s okay. A well-sealed hempcrete envelope will reward you with excellent thermal performance and comfort. By casting or placing hempcrete uniformly around the house, you create what builders call a monolithic insulation envelope – a continuous layer with no thermal breaks[1]. This continuous hempcrete layer keeps heat from leaking out in winter or seeping in during summer, and it avoids the thermal bridging issues that can happen with many conventional walls. The result is a home that stays naturally warmer in cool weather and cooler in hot weather, with minimal help needed from heaters or air conditioners.

Another benefit of concentrating on your hempcrete perimeter is that you inherently design for passive solar principles. With thick, insulating walls in place, you can then think about orienting your home for sun, adding eaves or shades, and other design tweaks – but none of those will matter as much if your walls themselves aren’t doing their job. So take Gary’s advice: get your hempcrete walls right first. A strong thermal envelope means your “hemp house” will deliver on the promise of cozy winters and breezy summers.

Energy Ratings 101: R-Values vs. Real-World Comfort

It’s common for new builders to ask, “What’s the energy rating of a hempcrete wall? How does it compare to regular insulation?” Gary’s answer is that it depends on the wall’s thickness and how you build it. As a rule of thumb, a 300 mm (about 1-foot) thick hempcrete wall might have an insulation rating around R-2.5 to R-3.5 (in metric units of m²·K/W). In fact, official sources note that a typical 300 mm hemp masonry wall will achieve roughly R-3.2 to R-3.5, which is a solid insulation value for most Australian climates[2]. By comparison, a well-insulated brick veneer wall is in a similar range, so hempcrete can hold its own in terms of basic insulation performance.

However, focusing only on the R-value (a measure of resistance to heat flow) would be missing the bigger picture. Hempcrete walls work differently than conventional insulated walls, and their true advantage lies in properties that R-values alone don’t capture. “A lot of people want their star ratings and the NatHERS ratings,” Gary says, “but what you’re doing with hempcrete, it’s a totally different way of building.” Traditional insulation materials (like fiberglass batts or foam boards) primarily block heat – they have high R-values but essentially act like a thermos, separating inside from outside. Hempcrete, on the other hand, offers decent insulation plus thermal mass and breathability. It doesn’t just slow down heat transfer; it also stores and releases heat in a way that regulates your indoor temperature more smoothly.

How does this work? Think of hempcrete as having a bit of “thermal inertia.” It can soak up heat energy when it’s warm and then gradually release it when temperatures drop. As one hempcrete expert explains, hemp-lime (hempcrete) “does more than reflect hot and cold energy – it absorbs, maintains and slowly dissipates that energy over a longer period of time, leading to more dynamic performance”[3]. In practical terms, that means a hempcrete wall helps even out the daily temperature swings. During a hot day, the wall absorbs heat (keeping the interior cooler), and at night it releases that stored heat (helping the inside stay warmer till morning)[4]. Your home’s temperature remains more stable, and you don’t have to crank the HVAC on and off as much to compensate for spikes in heat or cold. In fact, homes built with hempcrete have been noted to cut heating and cooling costs by up to 50% compared to conventional construction[5] – a testament to this material’s ability to reduce reliance on mechanical heating/cooling.

NatHERS Star Ratings vs. Hempcrete’s Performance in Practice

If you’re in Australia, you’ve likely heard of the Nationwide House Energy Rating Scheme (NatHERS), which gives homes a star rating from 0 to 10 based on their thermal efficiency. Assessors use computer models to predict how much heating and cooling a design will need to stay comfortable year-round, and they convert that into a star rating[6][7]. (For reference, a 0-star house would be unbearably hot in summer and freezing in winter, whereas a 10-star house should stay comfortable with almost no artificial heating or cooling[8]. Current building codes in Australia require new homes to reach around 6 to 7 stars minimum.) Naturally, new hemp builders are curious: can a hempcrete home achieve a good star rating?

The answer is yes – but again, the star rating isn’t the whole story. A well-designed hempcrete home can meet high NatHERS ratings, especially if you also incorporate good passive solar design, proper window placement, and so on. Hempcrete walls with R-3+ insulation values are certainly capable of scoring well in the software. That said, Gary points out that hemp homes excel in ways that the standard modeling might not fully account for. “If you’re doing a brick wall, say on R rating, your houses aren’t breathing,” he notes. A typical brick or brick-veneer wall might meet the required R-value on paper, but it’s a sealed system – it traps heat and humidity, and the indoor climate can quickly become uncomfortable without constant air conditioning or ventilation. In contrast, “what hempcrete does is controls the temperature and controls the thermals,” Gary explains. Hempcrete walls are often called “breathable walls” because they allow moisture and air to diffuse through them, which helps prevent condensation and keeps indoor air fresh[9][10]. Your hempcrete walls effectively buffer both heat and humidity, creating a more comfortable indoor environment that a simple star rating might not fully capture.

In a hemp home, you might find that even on a hot day, the interior stays surprisingly cool, and on a cold night, it doesn’t feel as chilly as the thermometer outside would suggest. This is the synergy of moderate insulation with high thermal mass at work. Meanwhile, the vapor permeability of hempcrete (plus the lime render finishes) means your home can “breathe” – releasing indoor humidity when needed – which contributes to that feeling of a healthy, pleasant atmosphere. Official resources note that hemp masonry provides very good insulation while being highly vapour permeable, resulting in “very comfortable buildings with good indoor air quality.”[9] All of these factors combined mean that the comfort level inside a hempcrete home can exceed what its raw R-value or star rating implies.

So, when you’re evaluating hempcrete through the lens of traditional metrics, keep in mind Gary’s insight that hemp building is “a totally different way of building.” Rather than chasing the highest R-value or a perfect 10-star design by conventional means, you’re building a home that works with nature: storing heat when it’s abundant, releasing it when it’s needed, and letting your house breathe. The end result is a steady, more naturally comfortable indoor climate. As long as your hemp home is well-designed (simple layout, well-sealed envelope, good orientation), you can have confidence it will perform on par with – or better than – a conventional home, even if the numbers on paper look unorthodox. And with experienced hemp builders like Gary proving these results in the field, you won’t be alone in navigating the compliance side of things. (Tip: When in doubt, work with an energy assessor or architect who has knowledge of thermal mass and hemp materials – they can help ensure your design meets NatHERS requirements while still capitalizing on hempcrete’s strengths.)

Key Takeaways and Next Steps

Building with hempcrete may require a shift in mindset from conventional construction, but Gary’s advice makes it clear that the fundamentals are straightforward. Here are a few key takeaways for aspiring hemp-home builders:

• Embrace Simplicity in Design: Start with a simple shape and layout. Fewer corners and straightforward plans will save you money and headaches. You can always get creative with finishes and interiors later, but first get the basic form right. Simple designs often perform better too, as they’re easier to insulate and seal properly.
• Seal and Invest in Your Hempcrete Envelope: Make the outer walls of your home the priority. Ensure your hempcrete is applied continuously around the whole perimeter with no gaps. This unbroken thermal envelope is what gives hemp homes their comfort edge. It’s better to spend on quality hempcrete walls now than to regret a leaky, under-insulated section later.
• Look Beyond the Metrics: R-values and star ratings are useful benchmarks, but remember that they don’t tell the whole story. A slightly lower R-value in a hempcrete wall doesn’t mean it’s inferior – thanks to thermal mass and breathability, your hemp home will likely feel more comfortable than a conventional home with the same rating. Build for real performance and comfort, not just for numbers on a report.

Finally, don’t be afraid to seek out expert guidance and learn from real examples. Pioneers like Gary Rogers and the team at Hemp Homes Australia have decades of experience building hemp homes in Australia. Their award-winning projects (including WA’s first hemp home and others that have won sustainability awards) show that hempcrete construction is not just eco-friendly, but also practical and beautiful. If you’re serious about building with hemp, consider reaching out to such experts or even visiting a hemp home to experience the difference. There’s a growing community and plenty of resources (workshops, blogs, and even other homeowners) eager to share knowledge about hemp building.

In summary, Gary’s guidance for first-timers boils down to this: keep it simple, get your hempcrete envelope right, and understand that a hemp home’s comfort can’t be measured by R-value alone. With these principles in mind, you’ll be well on your way to creating a hempcrete home that not only meets energy requirements, but truly excels in liveability – a home that breathes, stays cozy with minimal energy, and showcases the best of sustainable Australian building. If you’re ready to take the next step, do your research, connect with experienced builders like HHA, and dive into the hempcrete community. Your dream of a natural, comfortable, and energy-efficient home is within reach – and as many hemp home dwellers will tell you, the results are well worth it. Happy building!

Sources: Hemp masonry performance data[2][9]; Hempcrete thermal behavior insights[11][4]; NatHERS rating explained[6][12].

Hemp-Lime Passes ASTM R-Value Tests — HempBuild Magazine

Hemp masonry | YourHome

Building with Hempcrete: A Beginner’s Guide to Sustainable Construction | Margaret River Hemp Co

Thermal Star Rating | Nationwide House Energy Rating Scheme (NatHERS)