Very few MVHR suppliers offer proper ‘installable’ designs because very few install their own systems. Most transfer accountability to subcontract installers, who then inspect and commission the system, effectively marking their own homework. Not many designers can guarantee their systems will perform as designed after installation, or that the process of installation will comply with all associated regulations.
Compliance doesn’t just Part-F (ventilation), if you need to drill holes you it’s Part-A (structure), if you have more than two floors it’s Part-B (fire safety), if you’re close to a neighbour it’s Part-E (acoustics), if your pipes exit the building near a flue or chimney it’s Part-J (combustion appliances), if it’s a heavy MVHR on a suspended floor or is hung below a ceiling it’s Part-K (protection from falling), and if it uses electricity it’s Part-L1 (energy conservation). Regulation 7 applies to Workmanship and requires you to evidence the competence of those who work for you, and since 2022 there’s a new Part-O (overheating) regulation that may impact the ventilation.
There’s also a new Building Safety Act that says if any future occupant suffers a physical or financial loss as a result of something that doesn’t comply, the principal designer, builder, or more likely the home owner is liable for damages. Since 2022 there’s a lot more at stake, so maintaining design accountability is particularly important. The last thing you need is a hidden disclaimer that says “These drawings are for indicative purposes”, “Placement of [the materials] is for guidance only”, “company [name] disclaim any liability for work carried out”, or the old favourite “The design may need to be altered due to site conditions”, followed by “alterations are the responsibility of the installer”. These are all get-out-of-jail cards for designers more interested in the initial sale than the final outcome.
After you’ve checked their reviews, just ask; can you guarantee the installed system will consume less than 1.5 Watts per litre per second? Without the perfect design and then the perfect install, this mandatory requirement is the first thing to go, not that anyone will be checking.
Ask any experienced installer why they don’t like indicative designs, and the usual answer is ‘they just don’t fit’. Indicative designs are two-dimensional. They give you a plan view only and don’t account for varied floor levels or intersections, window and ceiling datums, often the direction and type of joists, steels, and other impenetrable structural elements. They’re just lines on a flat drawing to help someone work out what materials to sell you.
Even if it looks 3D when you get it, if it was designed in AutoCAD or any other 2D drawing package, it’s only a ‘3D render’ of a two-dimensional design. It’s not the same. For a system to fit exactly as intended, and therefore work as intended too, it has to be designed in three-dimensions from the outset. That means you need to start with a 3D model of the building in a design package like Revit. It adds a bit of cost upfront, but saves a lot of cost later when things start to unravel on site.
A 3D model means the designer can see all potential obstacles from all angles, effectively they can install the system virtually before pallets start landing on your driveway. Without that ability there’s an element of guesswork, and that means nasty surprises when you’re on site working to a tight schedule with one trade following another. As soon as the installer is forced to deviate from the design, they effectively become the designer and you lose accountability.
It’s impossible to guarantee the outcome unless you already know it’s going to fit perfectly.
Lets assume you have two options, a £300 design fee or a £3,000 design fee, which one makes the whole project cost less? You might think the first option saves £2700, but what happens when the installer needs a bag of extra bends just to get the machine into the plantroom. They can easily double the system pressure, and therefore double the running cost (forever), double the noise, and shorten the motor life. What happens when the neighbour complains about the noise from the intake and exhaust terminals pointing towards their property because the designer didn’t study the site plan? Dealing with the noise is expensive, moving the terminals is next to impossible. What if the installer says I need to run pipes through this void but there’s a steel in the way. The designer missed it because they didn’t overlay the steel plan on their 3D model. Do you wait for the structural engineer to approved new drawings from the architect, stalling other trades and causing grief, then attempt to plasma cut a hole on site and risk burning the place down? Do you lower the ceiling or box in the pipes, spoiling the aesthetics and causing untold knock-on effects? How about when the when the individual responsible for signing off Part-B (fire safety) points to a finished ceiling and says show me the fire dampers between this floor and the one above.
Not only are these problems costly, they’re also painful if you need to undo and redo a job, and they’ll spoil what should be a pleasurable experience. Now you’re wishing you’d invested the extra £2700 on problem-avoidance.
