Huge MVHR quote

[Garald]

Had two MVHR companies visit two months ago or so.

- The technician in company 1 said: this would be in the 10k-15k range, and heat recovery is something of which I am somehow skeptical, and you already have PIV. Le jeux ne vaut pas la chandelle (i.e., It's not worth it). If at some point you raise the roof, as you say is a long-term plan you are contemplate it, it could make more sense - then it would be more in the 8k range.

- The folks from company 2 were more enthusiastic, though they were quite frank that their MVHR recovers only about 30% of heat in practice (considerably less than the manufacturer claims, they said). Then they took forever to get back to me.

 

Just got a quote from company 2. Guess what - it's huge! Le jeux ne vaut pas cette chandelle!

 

Comments? Can you see anything funny?

 

(My immediate reaction is not to get MVHR for now, and rather wait until the next time I do truly major work (such as "raising the roof", which consists in "raising it" only in the sense that a caterpillar becomes butterfly - in fact the caterpillar mostly dies and the butterfly develops from cells that feed on the rest of the caterpillar), in the hope that the ca. 8k verbal quote from the first technician will be trueish modulo inflation, and that French technicians work with Passivhaus-standard MVHR by then.)

VMC DOUBLE FLUX HELFGOTT_Dossier.pdf Devis_020012278_HELFGOTT_Harald FOURNITURE ET POSE SYSTEME DE VMC DOUBLE FLUX LOGEMENT R+3.pdf

[Mike]

BT are having a laugh. On the plus side, the InspirAIR Top 450 Premium ERV is on the Passivhaus database, so there's absolutely no justification for the 30% heat recovery claim, and no reason to doubt that you'd be in the 80% zone. But €7,315 including VAT? You could buy one here for €3,464. If they've quoted list price for everything, no wonder the total is crazy.

 

Barring unusual circumstances, you also don't need the ERV version. ERV = enthalpy heat exchanger, which retains the moisture in the building. That's rarely chosen and may be a poor choice if you're expecting the MVHR to keep the structure free from excess moisture. They also cost more than a regular version; €1K more on the Aldes list price.

 

€8K for the other quote isn't cheap, but it is harder work retrofitting. If they've priced for the same MVHR unit, you should be able to negotiate down to the non-ERV version.

 

On the other hand, if you have room to add a big filter-box on the main air intake, I'd do that to save having to change filters to often.

 

Edited April 12 by Mike

[Garald]

So, I guess I should look for a third company? Or follow the other fellows' advice and wait for the hypothetical day (won't happen in the next 10 years I think, certainly not in the next 5 years) in which I raise the roof?

[Mike]

If I had the cash then I'd do it sooner to gain the benefits earlier. In which case yes, I'd firm up the verbal quote & seek at least one other for comparison.

[JohnMo]

Really what's the point, you will be several life times saving the money.

 

Is your building even that airtight to warrant going MVHR. It's got PIV now, so would doubt it. If it isn't pretty airtight, it's just additional ventilation, possibly where the 30% efficiency claim comes from.

 

Unlike @Mike I think it's a colossal waste of your money.

 

Just looked at some of your other ventilation topics, you really need to get on with what you have.

 

You have just completed a full renovation, so why do you really want the whole house pulled apart again?

 

 

 

[Garald]

25 minutes ago, Mike said:

If I had the cash then I'd do it sooner to gain the benefits earlier. In which case yes, I'd firm up the verbal quote & seek at least one other for comparison.

 

The verbal quote of 8k was not for now, but an estimate of how much it would cost to fit a MVHR system if I scrapped the entire attic and built an extra floor instead (since then there would be much less finagling around). Given that, it would be difficult to get a firm commitment. Let me try to get a third quote.

[Garald]

1 hour ago, JohnMo said:

Really what's the point, you will be several life times saving the money.

 

At this price point that would be the case.

 

1 hour ago, JohnMo said:

Is your building even that airtight to warrant going MVHR. It's got PIV now, so would doubt it. If it isn't pretty airtight, it's just additional ventilation, possibly where the 30% efficiency claim comes from.

 

See one of my other topics - I had an fan test done. (Of course the ventilation bits at the top of the windows got taped over before the test.) 

I got a score of 

 

Q4Pa-surf in m3/(h.m2) : 0,98

 

I got a long list of small things to fix, which I did fix. The guys who did the test eyeball that it's probably around 0.7 now (if I did everything right).

 

 

1 hour ago, JohnMo said:

 

Unlike @Mike I think it's a colossal waste of your money.

 

Just looked at some of your other ventilation topics, you really need to get on with what you have.

 

You have just completed a full renovation, so why do you really want the whole house pulled apart again?

 

Here's the summary of the story (I think some folks here have already heard it more than once).

 

Got into a major renovation project, never having done any house renovation before - this is the first time I own. Before you call me foolhardy, recall that (a) pretty much anything in the Paris area gets sold needing work, (b) someone who I trusted at the time recommended to me his supposedly genius architect (henceforth called by her initials, EB).

 

EB talked a good talk but seemed to have an iffy grasp of physics. She brought in a general builder who did a bit of everything.

 

At that point I found this forum (thank goodness). People here taught me a great deal. I managed to get EB to accept some input in the choice of insulation materials, though for reasons that were not apparent to myself or the general builder, she absolutely refused to consider insulating from the outside (even though losing m^2 of indoors space in the Paris area means losing lots of money).

 

EB had bizarre prejudices against heat pumps. She also didn't think I should aim at getting anything higher than an energy rating of D (we started out at F), her argument being that D was the average result of a renovation. That was a very strange argument - why not aim at being much better than average?

 

EB had a strange plan on how to install a heat pump. No installer wanted to accept it. I asked for a sketch and posted it here. People were soon ROTFL and explained well why it would be a total disaster.

 

Explained everything firmly and politely to EB, whose already nasty manner became worse. She started asking for more and more money, including for things she hadn't done yet. She also started showing up hours late to meetings, or failed to show up.

 

At some point, she asked for more money than had ever been agreed upon. I made clear things couldn't go on like that, and she just left. The contractor was in a terrible mood but stayed until the end to finish the job.

 

At around that time, I was telling all of the above to a friend, who asked a question that should have been obvious in retrospect: have you checked that she's really an architect?

 

Guess what - it was quite easy to verify that she was not a member of the Order of Architects and hence had no right to call herself one. It took quite a bit more time and effort to verify that she had never had an architecture diploma. Over time, the picture has become clearer: she took classes in interior design in the 90s (but apparently never finished), got an internship in an architecture studio run by one of her lecturers, was an assistant in an architecture project in the late 90s (she made the architects in the project believe that she was an architecture student), then had some sort of job at another architecture studio, then got some sort of cheap master's (Saturdays only) on urban planning in the late 2000s, and set out on her own career as a fake architect.

 

But all of that I learned over time. In 2023, my focus was on finishing the renovation. Did all heat losses computations myself with the help of the trusty Buildhub spreadsheet, and convinced the general builder that old cast iron radiators can work perfectly well with a heat pump running at medium-low temperatures. (When it comes to understanding heat-pumps - many thanks are due both to Buildhub and to Feynman for one of his first-year lectures on physics: if you read it backwards (well, reversing the direction of the arrows), you understand everything.) Got an energy rating of B in 2023.

 

Since then, I've been improving things here and there: while it is my impression that the general builder was reasonably honest and mostly competent, he did some things much better than others. By now, I know a good plumber, a good hardwood person, etc. It is clear that I will have to fix some things that should have been fixed while the renovation was ongoing (e.g., the plumbing in the kitchen is not just malfunctioning but illegal; the plumber implies I should not worry too much about the last bit, as half of the plumbing in Paris is illegal, and the rest is mostly substandard).

 

The question now is when to stop. (Here the fact that I don't have much money left right now helps.)

 

What I am leaning towards is:

in the short term,

(a) fix the plumbing in the kitchen; let amateurish plumbing elsewhere be for the while being;

(b) get a quote for insulating whichever bits of the heating/hot water pipes can be insulated without ripping things apart (the fake architect was very much against insulating the pipes for whatever reason)

(c) if I get a reasonable quote, insulate the attic ceiling properly. This is the weakest part of the entire insulation (it was the *only* bit that was insulated when I bought the place - the owners before the previous ones got that bit done with fibreglass 15 years ago) and one can really feel it, particularly during the summer. *Of course* I should have got it done before the attic got painted, but then it would have been done by the general contractor, and I don't know whether he'd have done it well or badly. And there's also another factor at play - see below.

 

Oh, and also get a (real) lawyer, but I've already done that. I also found where in the provinces EB is hiding (she left Paris).

 

In the long term (>5 years), I can consider:

(i) insulating the northern wall from the outside; this is something that needs to be decided by the coop as a whole, but it's a tiny coop - a couple and I are the only ones who ever show up to meetings) and we are all leaning that way. (The northern wall was insulated from the inside using a mixture of reflective insulation and insulation that actually works (the fake architect just put two things together; I don't know whether will ever be condensation.)

(ii) if I have money, money, O!, I could 'raise the roof', i.e., recreate the attic as a space in most of which I could actually stand. That would of course involve destroying at least half of the current roof, and probably losing all the money invested in (c) above (companies are loath to reuse insulation material installed by other companies). OTOH it would increase the value of the property a great deal. (Prices around here are determined mainly by the number of m2 in which a 180cm-tall person can stand.)

(iii) MVHR is probably best left to this stage (redoing the entire attic would simplify matters, or at least that was the position of one of the two companies I consulted), but I'll get a third quote. Note the other company is of the opinion they can install MVHR without ripping too many things apart, but they are the ones asking for lots and lots of money.

 

This general plan would seem to make sense, though at the same time I don't know how to escape the (c) vs (ii) dilemma. And, of course, if I got a reasonable quote for installing MVHR now, that would change matters (I'm not optimistic). There's also the matter that the coop will probably be ready to do (i) in about 5 years (we'll probably get all courtyard-facing walls insulated in one go); perhaps (ii) and (iii) should be postponed indefinitely, except that it would make sense to do (ii) at the same time as (i). Oh well.

 

 

 

 

 

Edited April 12 by Garald

[Garald]

Hm, that summary turned pretty epic - I'm almost tempted to make it into its own thread for easy reference. But what category would it fall into? "Summary of personal building journey"?

[Sparrowhawk]

On 13/04/2025 at 00:06, Garald said:

Hm, that summary turned pretty epic - I'm almost tempted to make it into its own thread for easy reference. But what category would it fall into? "Summary of personal building journey"?

The "Welcome forum" as a "Retrospective on my journey" thread?

[Garald]

45 minutes ago, Sparrowhawk said:

The "Welcome forum" as a "Retrospective on my journey" thread?

That’s what I went for!