Walk into a house that was just finished and you'll notice the "new house smell." Part of that smell is VOCs, or volatile organic compounds. They come off adhesives, joint compounds, paints and insulation, and they end up in the air you breathe. Formaldehyde is one of them. For indoor air, the World Health Organization sets a guideline of 100 µg/m³ (30-minute average). IARC puts it in Group 1, carcinogenic to humans. What counts is how much of it is in your air, and for how long.
In this episode we compare two ways to build a wall. We won't rank them, and we won't try to scare you.
The whole build-up counts
A drywall partition goes up in layers: metal studs, plasterboard, mineral wool insulation, joint compound, adhesive, paint. Every one of those layers can release something. Most of it comes out in the first days after installation. Then emissions drop.
That's why materials go into a test chamber under the EN 16516 method, with readings at 3 and 28 days. The 28-day number tells you what's left after the first month, when people are living in the house. Italy's minimum environmental criteria for construction (CAM) call for tests like these.
Many certified mineral wools now use binders with no added formaldehyde. A drywall wall built with certified products can also perform very well. So you judge the whole wall. Boards, adhesives, joint compounds and paints all add to the total.
And a hemp-lime wall?
The HES system that H0ME is bringing to Italy uses a mix of hemp shiv and lime (US patent 10,266,451 B2). The finishes have to be breathable mineral products. For how it works, read how HES Mix works.
But "natural" doesn't mean "zero emissions." Raw hemp shiv, like a lot of plant fibers, can give off compounds of its own, such as terpenes and natural aldehydes. The lime around it should work as a buffer and a mineral barrier. That has to be measured. We can't just assume it.
Here's a limit we won't hide. The HES technical dossier has no VOC test report specific to HES Mix. So today we can't tell you this wall emits less. We can tell you how it should be measured, and we will measure it.
What this means at home
The wall is one piece of it. Three other things matter.
- The finish. Put a synthetic paint over a hemp-lime wall, seal the pores, and the advantage is gone. It needs breathable mineral finishes. More in a wall that breathes.
- The furnishings. New furniture, glues and rugs give off VOCs too. That adds to what the walls release.
- The air. In the first few weeks, airing the house out often helps clear emissions.
Keep two things apart. At the "G. Rodari" school in Rossano Veneto (2016), the HES system recorded −27% indoor CO₂ across two identical, monitored classrooms (HES network data). CO₂ tells you about air exchange, not VOCs. The figure is useful. It says nothing about chemical emissions.
What we'll do
H0ME has been a general contractor in Avellino since 2019. We haven't built an HES home of our own yet; the first site is being prepared. We'll measure VOCs there at 3 and 28 days and publish the results here, whatever they show. Even if the numbers look worse than we hoped.
FAQ
Is drywall bad for the air in my home?
No, as long as it's certified and installed with low-emission products. The whole build-up counts. Adhesives, joint compounds and paints matter as much as the boards.
Does hemp-lime emit zero VOCs?
We can't say. Hemp shiv can give off natural compounds, and the HES dossier has no VOC test specific to HES Mix. We'll take measurements at our first site.
What can I do to breathe better in a new home?
Pick products with emissions certification, mineral finishes and low-emission furnishings. Open the windows often in the first few weeks.
Want to see how the technology works? The technical data is on our Technology page. Previous episode: Suppliers: how we choose who produces the hemp shiv. Next episode (EP16): one week from now, on a Friday again.
Article produced with the support of artificial intelligence and reviewed by the H.0.ME. editorial team.