PassivHaus

[Mikesolar]

Originally Posted by AC_Hacker

How broadly is the convention accepted?

Is this a convention that is only seen in the Canadian boiler industry?

Is the US boiler industry also using this convention?

Have you ever seen it anyplace else?

I mean, if it is confined to the Canadian boiler industry, and since this forum is regularly read by a world-wide audience, maybe referencing your frame of reference would be useful in avoiding confusion.

Maybe something like:

7kWh x 3.412btu = 23.8Kbtu or, 23.8Mbtu CBS (CanadianBoilerSpeak)

Just a suggestion to avoid any intercontinental confusion.

-AC

Very broadly, Look up Viessmann, Weil McLain, Laars, Burnham, etc. All the boiler companies do the same thing.

[AC_Hacker]

Originally Posted by Mikesolar

I brought this up because I am working on a 3 floor, 380m2 passivHaus and we are struggling to select the heating system. The owners are leaning towards radiant tubing and 40mm of thermal over pour (gypcrete) even though it is a high cost for very little heat output. It does, however, make the heat very even and has other benefits (sound and fire).

I was wondering about this part of the project...

If this actually is a passive house, the heating need should (by design) be only occasionally required, and when the heat is required, it should be very, very modest. The whole rationale behind Passive House is that no heating system is required at all. That is why it is "passive".

For instance, your comment about the heat being very even... if you mean spatially even, like, "the floor will feel warm all over."

The floor will not feel warm anywhere, because the heat needs will be so low, that the temperature will never be high enough for bare feet to ever sense warmness.

HERE_IS_A_LINK that explains why this is the case.

A lot of people who want radiant floors are led by the dream of warm feet in the winter.

If your radiant floor got warm enough to feel warm on the feet, AND if it actually is a Passive House, your client will have to throw open windows in the winter to keep the room temp at a comfortable level... This would completely cancel out the work that their ultra high efficiency (and very expensive) HRV is doing. They will be cursing the person who put in radiant floors all the while.

-AC

[Mikesolar]

And "therein lays the rub" as the bard would say......the floor will not be warm to the touch at all. It will be just above body temp if that. The problem with the ductless in a larger house is distribution and the open/closed door issue. The radiant eliminates this issue, but at a cost. The HP that heats this water will be efficient indeed but seldom used. Most of DHW will be from an oversized drainback solar system which I suspect will account for 80%+ of the load.

I read through the Oregon paper. Most of it is not news to me and I have designed the floor heating with this in mind. The floor will move solar heat to the colder areas but given the high insulation levels, it will all be VERY slow. I suspect that the radiant is not all that necessary but some method of even heating is necessary in a large house. If it were smaller, I might not do it and maybe just do bathrooms and let the HRV move the heat around.

Plus...I gave them all the options and the reasons behind them. PassivHaus owners, it seems, really do like to get into the nitty gritty of the house. They are not "passive" owners, haha

[AC_Hacker]

Originally Posted by Mikesolar

...I read through the Oregon paper. Most of it is not news to me and I have designed the floor heating with this in mind...

This whole thing just sounds wacky to me.

I mean, is this just a nice, well insulated house that somebody is calling a Passive House, or is it actually a Passive House?

The object of a Passive House is to design it so well that not heating system is required.

They developed the method in Austria, so it can be done.

In other words, you, Mikesolar, are out of a job.

If it needs occasional, minor supplementary heat, that is one thing.

If it needs a heating system, it is not a Passive House.

Now, if the owners have more money than understanding, and they want to invest money in a heating system which has no purpose. I guess that is their prerogative.

So, if you are designing a radiant floor for this place, you have obviously already done a heat gain/heat loss analysis, no?

What did you come up with in that analysis?

-AC

[Mikesolar]

First, the engineering was done by a committee of accredited PassivHaus designers (not me, I came in later) and if you read the literature, they are all different and all need some form of heat at some time. I'm not out of a job because I do much more than heating. The ERV is integral in this process, there is still a heat load and a cooling load and if you read the requirements, the load must be less than 15w/m2 which this house is.

No house is perfect and this one has, amongst other issues, a couple of evergreens that shade things a bit (for example). It is bigger than the average house of its type so the issues are compounded somewhat. It will house 7-8 people so it will have a higher than average DHW load and will have more load swings than a house with 2-3 people. The heat/cooling loads were done by 3 different companies, including WattsRadiant and they all came within 15% of each other (which is unusual).

No one is flying blind here, but for every problem there is 10 solutions and you have to narrow it down. As I mentioned before, even heat is important and more difficult to achieve with a group of ductless HPs so a compromise was made.

[Ormston]

Originally Posted by Mikesolar

if you read the requirements, the load must be less than 15w/m2 which this house is.

Is that a typo or has some correction factor been used to increase it?
I thought it was 10w/m2?


AC
Should you not be aiming for the EnerPHit (retrofit) standard of 25kWh/(m2a)?


Steve

[randen]

Nothing on TV so I'm playing with the math. Were do we fit with the Passive Haus??

House 3600 sq. ft. or 334.0 sq mtrs.

334.0 * 120kwhs= 40080kwh/yr. or less for Passive Haus designation.


If we explore only heat the envelope for the home I will have to go back to my records of heating with the very bad, very neanderthal oil heating.

We used depending on the heating season 340 ltrs to 284 ltrs per month for a years heating

Lets use the worst case. 340 * 12= 4080 ltrs / year.

We heated the floor with a domestic oil fired hot water heater. I checked the manufactures spec. and it fires between 77-80% efficiency

The conversion of a liter of heating oil to kwh's is

4080 * 11.69 = 47695.2 kwh/yr input of oil

47695.2 * 0.785 (efficiency median) = 37417 Kwh's output of heat from water heater.

Would this indicate that we have qualified for Passive Haus???

37417Kwh's is less than 40080Kwh's


Now I must add that the heating oil used also included domestic water heating in the consumption and not only heating the envelope. But even including this as a worst case we still make it within the Passive Haus criteria.

Where we have missed the mark is the air infiltration. The house was subjected to a blower door test twice and the end result after a little more concentration on sealing the envelope we obtained a reading of 0.92 ACH@50 pas. Passive Haus requires less than 0.60 ACH

If I check the Canadian building code a typical new home would obtain a rate of 4-5 ACH. and for sure more attention to detail would lower this rate. It seems to me that the general population that purchase homes here, don't request any more performance in their envelope. The granite countertops and bathroom fittings and that large wall for the flat panel TV are the main concern. I guess natural gas is still really inexpensive.

The fun part came when I applied the Kwh consumption for electricity now with Geothermal and any help that the solar hot water would offer. The COP of say 2.5 to 3.5 would mean I get 2.5 to 3.5 * the amount of heat for the Kwh energy used. Being I don't have a method to measure what amount is used just for heating the envelope I can't use any numbers for qualifying The Passive Haus.

BUT last years usage was 30812 Kwh's everything in!!! Using that-- very Passive Haus.!!!

Passive Haus extremely close. On Slab heated concrete floors Love them!! Geo-Thermal saved my Butt!!! Good windows and doors, indispensable. Attention to envelope sealing, just really smart (costs very little). Exterior insulation foam and stucco another great idea. Lots of glass on the south facing wall really nice when the sun shines The same for the solar hot water Free heat anyone??

Any one pushing forward with construction projects. Push the insulation and sealing. It's well worth the extra costs maybe its hard to justify building above code this year with the cost of energy today but what will the cost be in 10 yrs???

Randen

[Ormston]

Originally Posted by randen

Nothing on TV so I'm playing with the math. Were do we fit with the Passive Haus??

House 3600 sq. ft. or 334.0 sq mtrs.

334.0 * 120kwhs= 40080kwh/yr. or less for Passive Haus designation.


If we explore only heat the envelope for the home I will have to go back to my records of heating with the very bad, very neanderthal oil heating.

We used depending on the heating season 340 ltrs to 284 ltrs per month for a years heating

Lets use the worst case. 340 * 12= 4080 ltrs / year.

We heated the floor with a domestic oil fired hot water heater. I checked the manufactures spec. and it fires between 77-80% efficiency

The conversion of a liter of heating oil to kwh's is

4080 * 11.69 = 47695.2 kwh/yr input of oil

47695.2 * 0.785 (efficiency median) = 37417 Kwh's output of heat from water heater.

Would this indicate that we have qualified for Passive Haus???

37417Kwh's is less than 40080Kwh's


Randen

Is the 120KWh/yr not the figure for everything EXCEPT heating, as in cooking lighting TV etc.

It's 15KWh/yr for heating.

So 334 * 15 = 5010KWh/yr

Unless 86.6% of that oil was burned for DHW not heating then it doesn's sound very passive haus.

Steve

[SDMCF]

Why do you take into account the efficiency of the oil burner? I don't know much about it but that doesn't sound correct to me. Surely it is defeating the object of the PassivHaus standard? Take an extreme case to illustrate the point. If someone tried to sell you a PassivHaus and explained that the heating boiler was only 10% efficient and so the house really does qualify, would you want to buy the house?

[randen]

Steve

You are right. I went to a couple other sites and check the qualifications for the Passive Haus. Indeed 15 kwh/sq.m/yr. for heating alone.

I was mistaken.

The 120 kwh/sq.m/yr is total consumption.

With the total criteria of 120 kwh we are quite efficient. with efficient appliances and all LED lighting and other measures we fall in there. But yes for heating measures we are over the set criteria limit.

We did not meet the Passive Haus criteria but with the geo-thermals humming plus the odd day of free heat from the solar hot water collectors and a tight well insulated envelope. We are elated.

Randen