In summer some houses heat up all day and never cool down, not even at night. In winter the cold comes through the walls before the windows. The HES system, which H0ME brings to Italy, shifts heat by 18 hours through a 320 mm wall: so says the HES technical data sheet. The warmth of two in the afternoon arrives indoors around midnight, once it has cooled outside.
But before it becomes a wall, that physics passes through a spec. Say "bill of quantities" and most people picture columns of numbers and prices per square metre. Not yet. On the road to H0ME's first home with HES technology, the engineer has reviewed a draft with five main technology items: what goes in, how it's installed, what performance it guarantees. No costs. Prices come later, with the site under way.
In the previous instalment, Hygroscopicity, Explained With a Glass of Water, we saw how the wall absorbs and releases vapour. Here it becomes spec lines.
The Physics on Site: The 5 Line Items
1. Hemp shiv. The woody core of the hemp stalk, chipped into granules. Particle size decides how well the wall insulates and how porous it stays: see hemp shiv particle size. On a spec, "hemp shiv" isn't enough: the required chip size has to be written down.
2. Lime as the binder. It holds the hemp shiv together without sealing it. Unlike a cement binder, lime lets the material breathe. The shiv is porous and lime doesn't close its pores: everything else follows from that, as in the hemp-lime mix.
3. Timber frame. The load-bearing wooden skeleton the hemp-lime mix is cast around. The spec sets its sections and spacing: the frame fixes the final thickness. At 320 mm we're back to the 18-hour lag.
4. Skilled installation. This is where the labour is paid for. The wall is tamped by hand, in layers, with a precise technique. A bad job throws away the performance, however good the materials.
5. Breathable finishes. The final plaster has to let vapour through as readily as the rest of the wall. One that's too impermeable cancels out the work of the other four items. We wrote about it in the wall that breathes.
Who Has Already Used Them
The spec isn't new: the HES network has been building this way in Europe for years, with documented results. As of 31 December 2014 it had built 27,653 m² with this system (source: HES Group). At the "G. Rodari" school in Rossano Veneto (Vicenza), in 2016, a comparison between two identical classrooms measured 27% less indoor CO₂ in the HES one. At the Fortuny Museum in Venice, FLIR thermal imaging two years after installation found no delamination or degradation. These are HES network figures, not projects signed by H0ME: we cite them because they show the five items, when respected, hold up over time.
What It Means at Home
Beyond the thermal lag, the HES technical data sheet gives the system H0ME brings to Italy a conductivity of λ = 0.048 W/(m·K) and energy class A4 at 35 cm thickness in climate zone D. Fire reaction is B-s1-d0 CE under standard LVS EN ISO 17050-1, measured by Vilnius Gediminas University and BRE, University of Bath. A spec that skips an item, or describes it vaguely, risks missing those numbers on site. That's why the items come before the prices.
H0ME has been a General Contractor in Avellino since 2019. H.0.ME. has been the Italian licensee since 2019 of US patent 10,266,451 B2 (PCT/CH2015/000085), the basis of the HES system. H0ME's first HES site is in preparation: not yet built, not yet sited. Here we describe the draft spec that precedes it, not a building already standing.
FAQ
Does a spec with these five items apply to any HES home?
The technology items are the structural ones of the HES system. Quantities and sections adapt to each project.
Why are there no prices?
Because the first site is still in preparation. Publishing estimates now would mean giving them as final when they aren't.
Is skilled installation a materials item or a labour item?
Labour. It gets its own line because the tamping technique weighs on the final performance as much as the materials.
The full technical data sheet is at /tecnologia/. The previous instalment is Hygroscopicity, Explained With a Glass of Water. The next is in preparation.
Article produced with the support of artificial intelligence and reviewed by the H.0.ME. editorial team.