I'm planning a moderate size home in SoCal in a semi-desert climate with adequate thermal mass. The home will have a tight envelope and my understanding is that some sort of ventilation system with separate duct work is required.

I was planning on an air-source heat pump to meet heating and cooling needs, but this will only be used in the summer and winter months mostly.

Does anyone know if there is a manufacturer that makes an energy efficient, dual HVAC/ ventilation system that would satisfy both of my needs and eliminate the need for 2 duct systems?

I am using minisplits in Central Oregon, with a well insulated tight new home, No duct work required. We have one in the main open area, and a second small one in the master br.
There is no more than a 3 degree temperature differential throughout the 2350 Sq fT "L" shaped house. Usually less than 1.5 degrees unless it is below Zero Outside.

The duct work for the HRV Is just insulated flexible duct, not a big deal. BTW I would never build a home without the HRV, I love it. Only about 10 degree heat loss incoming vs ambient.

Thanks for the info.
I'm assuming the house is all on one level. That's good to know. I was thinking a similar configuration but thought that more than 2 minisplits would be required.

But in Central Oregon, do temps reach 100 during the summer? I'll be dealing with a semi desert environment.
And during those day that don't require heating or cooling, the minisplits work as a ventilation system?

Minisplits do nothing for ventilation. The air that is heated or cooled is room air - they do not bring in outside air, which is why you do need a separate ventilation system.

And there are the Lunos units if you do not want ductwork.

https://foursevenfive.com/product/lunos-e²/

Posted By Bob I on 19 Jan 2017 12:35 PM
And there are the Lunos units if you do not want ductwork.

https://foursevenfive.com/product/lunos-e²/

Bob, We've got a cabin that is pretty air tight that heats with a wood stove. To keep air flowing in, around, and through the stove & up the chimney I just crack a window. Seems to work just fine & was easy and inexpensive. Does the Lunos fan system offer something more than just cracking a window a bit?

It is a heat recovery system, so you get air that is warmer than outdoor temperature, unlike your window.

Thanks for all the response.

Does anyone know about this? CERV - http://buildequinox.com/

It seems to be a dual system with integrated HRV/ heat pump for heating, cooling and dehumidification using one system of duct work.

It's probably the more expensive option. I haven't looked into it.

Lunos seems to be an affordable option that doesn't just exhaust air but also brings fresh air in. I wonder if it would be possible to have them in hallways and centrally located instead of every room as pictured on their website.

It seems though as building codes around the US require tighter envelopes in the future, and temperatures become more extreme everywhere, some sort of economically viable, integrated system will be necessary.

CERV has been around for a couple of years. A Net Zero modular builder, Ver-Mod, has used them and is very pleased with the product. They are not inexpensive, but do combine a couple of functions usually handled by separate systems.

This is one of the first of the American made devices designed and built for the new "net zero" class of homes. The more houses of this type get built, the more new products will be developed. There are, for example two new American window manufacturers building European style Tilt Turn windows, although one just announced it's closing since the market isn't developing as fast as the German owners wanted. At this point we have to use what is available.

Thanks Bob.

Posted By minotto disegno on 18 Jan 2017 02:27 PM
I'm planning a moderate size home in SoCal in a semi-desert climate with adequate thermal mass. The home will have a tight envelope and my understanding is that some sort of ventilation system with separate duct work is required.

I was planning on an air-source heat pump to meet heating and cooling needs, but this will only be used in the summer and winter months mostly.

Does anyone know if there is a manufacturer that makes an energy efficient, dual HVAC/ ventilation system that would satisfy both of my needs and eliminate the need for 2 duct systems?

<!--[if gte mso 9]> If you're looking to be misled, you have been so far. I’ll try and set you on the right path since I’m a Cali peep too

Ventilation…

Anyone that thinks or suggest you build an air tight home w/o knowing what you are doing does not know what they are doing or suggesting. Most get it wrong, think air will de-tox toxic building materials, chemically make them inert and stable by some miracle....some even think that they have to have symptoms, if they don't everything is fine. Plenty of unseen toxins that produce none until it’s too late, like cancer.

Uninsured DIYs designers take on personal injury liability. You'll get all the ill-advice you want on green sites, the problem is they won't be there to hold your hand in court. Check out the lucrative booming IAQ corrective action business on the internet.

You need a COMPLETE understanding of ASHRAE 62.2 just for starters, preferable prior builds in accordance with to advice. 2016 is out and the fact nobody has mentioned it tells you they are not pros. In it you’ll find what I stated above as disclaimers.

In it you'll also find required OAQ test per NAAQS to determine if a ventilation sys is possible and, all kinds of local outdoor intake air & separation restrictions to meet, pressure & flow rates, or it could be VERY damaging to occupant’s health. 

Also, that in Z1-2, sounds like you are in 2b(hot/dry), you don’t need mechanical ventilation you can use window method unless you mechanically cool, OR, you have a heated building (natural or mechanical) for less the 876 hours/yr. If you do need one you have to calculate the flow rates and there is a natural air credit depending on blower door test or one of 5 ways to calculate it.

Thermal mass is handled different than highly insulated in dry climates. You’ll focus on HRVs vs ERVs.

Once you understand the whole house and local exhaust (bath/kitchen, etc) requirements then you shop.

There are also variable/continuous & real time vent combi systems. …. Then you have to decide if you want your health in your hands, or auto-scheduled in accordance with a controversial std.   

These are good certified products: http://hvi.org/proddirectory/

Then the system has to be further tested beyond the blower door to verify it to the std, to verify contaminated air is not being infiltrated, back flows, etc. If a ductless like Lunos, Zehner, Vents-US is used no more than 10% tested by manufacture, so you have to know what to look for.

HVAC

You can design a ducted air-source HP tied to ventilation systems, may make better sense if there are existing ducts and one does not have easy access to run minisplit refrigerant lines.

or, you go ductless splits best for new construction.

Zoned systems are best. You have to determine peak heating and cooling loads first using ACCA manual J8 or ASHRAE RLF.

A little history,

The physics involved in the transfer of heat and energy between buildings, occupants, and the environment is quite complex. The most current and best math models of this problem require significant input data and thousands of calculations in an iterative process. The calculations are so involved that researchers have been forced for years to create various simplified procedures that are doable by hand or within reasonable calculation time on a personal computer. The cost of these simplifications from the theoretical best math models is accuracy, especially residential.

Problem with MJ8 most popular is the way it handles walls/roofs/glass, thermal mass, ventilation, & other assumptions. Now making it less accurate we have thermochromic glass with SHGC ranges. It also uses weather conditions not local TMY weather towers, hard set points, allows oversizing compared to load which is often the case.

I use EnergyPlus and WUFI computer simulations for hygric loads. It blends all building component loads, and I can compare designs for optimization. I’ve seen as much as 40% difference between simplified MJ8 & complex E+ simulations. Right now I have one MJ8 is estimating 33,000 BTU/hr, E+ 12,000, so I weigh that w/MJ8s successful track record vs more accurate whole building E+ computer sim. MJ8 is typlically 15-20% higher. Manual S places limits on oversizing or under can lead to issues especially dehumidifying/cooling.

So my MS design for a 2348 SF two story loft is 4 zoned, one 12K, (3) 7K (two of which are daisy chained to other rooms), BTU HP units….there is no need for excessive temp differences between rooms. Open vaulted 18 foot peaks costing ~ 8K BTU/hr.

Minisplits are sized for peak cooling loads or heat removed both latent (low in dry bulb climates with thermal mass like you) and sensible…..In my and your cases it exceeds heating, if not it can be sized for cold climates retention.

Cerv is an demand control (DCV) ERV with limited misleading IAQ monitoring, not whole house HVAC, again as noted above and in ASHRAE 62.2 requirements for. Rare you only have < 5k btu/hr loads. Today, we have better IAQ monitors...another complex science only WUFI_BIO can pre-determine with proven high levels of accuracy.

Not to scare you off but be warned when it comes to your health you may want to seek pro-advice and pay as required for it.

Good luck!

<!--[if gte mso 9]> Normal 0 false false false EN-US X-NONE X-NONE

To Answer your question, Yes temperatures will hit 100 in Central Oregon in the summer, but that is rare.
Colds temps are not rare, We have been below zero about a dozen times already this year, bottoming at -25.

Another advantage to the ducted HRV's are you can eliminate required Bathroom, and desired Laundry fans, and also design the layout of the ducts to draw from rooms that you want to circulate Conditioned air into.
For instance my HRV intakes are in both baths, laundry, and One bedroom, that are the farthest from the minisplits. This draws heated air to them. the HRV return duct goes into the open great room, and circulates the return air, mixed with Conditioned air throughout the room.

The only advantage of ducted ventilation systems these days is about half the initial cost because they are unsafe junk and obsolete & pros know it. A ductless system transfers flows & pressures between rooms/outdoors MUCH more efficiently. IF you are transferring dust, moisture, PM2, microbials, CO, C02, fire & smoke, between rooms in a highly air sealed building you designed your death certificate which is 9xs out of 10 due to lack of professional BIO/CHEM analysis moreso with ducted systems.

The simplest way to determine if an ERV makes more sense is look at lb/lb indoor/outdoor humidity ratios & infiltration CFM @ ACH50

You can get double duty and greater efficiency by combining central HRV and exhaust ventilation. Mine draws through a ducting distribution box and power-open dampers, so that it exhausts two bathrooms, the kitchen and the laundry closet (condensing dryer) on demand. For timed operation, I use a fifth power damper mounted in a central chimney chase.
The bathrooms clear in a normal timeframe. While the kitchen vent, per manufacturer's instruction, must be 10 feet from the cooktop, it also performs acceptably. Made roux for gumbo last week. Missus didn't even notice. Two cautions. Use count-down timers rather than switches because exhaust is quiet onto unnoticeable. While some of the longer runs will call for large ducting, I used 6 inch throughout assuming that short, intermittent use won't stress fan motors unduly. So far so good. Your mileage may vary.

Sounds like high watt power consumption not needed. 175 watts @ rated SRE max for most Passive Homes < 2500 SF.

ASHRAE 62.2 requires dedicated exhaust for toxic gases from kitchen hood, or other rooms where combustible appliances (dryers, fireplaces, water heaters)/potential back drafts are exhausted and separation requirements that are tested on site, including lint from dryers that produce 1000s of fires/yr and collect humid non-visable PM2.5 for distribution in ducts/rooms. Pressure walls may have to be tested for separation. Heavy or orderless toxic gases don't always evacuated by air flow, so just because an area "clears" of odor does not mean they are gone. No need to put any rooms under negative pressures to move temps or get the same flow effects. The rooms and ducts should be commissioned properly. Ductless do this best at low CFM/Power.

For high flow ducted systems ceiling multi-zoned minisplit handlers today can be connected to other registers, ERV/HRV air, no need for room temp differentials or temp stack effect. http://www.lg-dfs.com/ceiling-cassette.aspx/LC187HV

All electric house. As mentioned, condensing Miele dryer and a hypervigilant laundress. No toxic gases, heavy or otherwise, although the missus may disagree. The chimney chase has two fans: 200 cfm in and 160 out. I just assumed that GBT readers would smart enough treat combustion appliances with more thought, but then again I'm not trolling for fees. But thanks for your concern.

Minisplit cooling over a slab on grade is a nobrainer, absent unusual heating events like west windows. I have little variation in a distant den and bathroom even with doors closed.

Posted By toddm on 25 Jan 2017 02:31 PM
I have little variation in a distant den and bathroom even with doors closed.

Todd, I'm glad you mentioned the small variation in temps, as I have always wondered how/why Mini Splits can accomplish that. Can you explain please? I have a cabin, with a very open floor plan. It is heated by a great wood stove. We have a ceiling fan that works great to move the warm air about - but the bathroom and back bedroom stay cold. There is a small hallway that accesses those two rooms, but this is a small cabin too - yet those two rooms need additional heat. Could / would a mini Split warm those two rooms?

Alas a slab on grade only works for cooling. Cold air sinks to the floor and rolls into distant rooms. Even with doors closed, the concrete itself conducts cold and cools the rooms. By contrast, warm air rises. Worse, because the slab gives up heat to the ground, and to the rooms when your cabin is unattended, the concrete chills the cabin during the winter as well, and more so every day as the winter wears on. Mine is a radiant floor heated directly by a wood stove boiler. Before I got the hydronic going, my two-ton minisplit was like spitting into the ocean.

Woodheat.org has tips on circulating stove heat. Otherwise, rugs and a minisplit.

For the rest of the readers: Plenty of current high performance homes in cold climate running minisplits only no carpet no HR no cold concrete floors if designed properly.

As I already stated when it comes to air tight homes and ventilation seek a qualified pro(s) that fully understand OAQ/IAQ.

There is NO WAY to understand both without being designed and tested by a pro. The best scientist still to this day after five years are debating them, baffling how the average DIY persons above understand them. The best answers are found on ASHRAE website and in 2016 62.2.....or on AVIs website. BSC is another. Not here!

You won't find ductless in those standards but the same rates apply for sizing the systems. Luno uses lower .01 SF factor, to be more conservative use 62.2 .03 as denoted on their site that needs more watts,

https://foursevenfive.com/sizing-lunos-e2-through-wall-ventilation-units/

Because there are multi penetrations watch total system power consumption @ rated SRE. The DC motors can be PV tied to improve that.

Be safe rather than sorry and good luck since you'll need some of that too....

Actually this is one case where overdesign proved to be far superior to engineering. My slab sits on 4 inches of xps (R20); it was poured inside ICF frost walls R22), and topped with 12 inch AAC block (r16). Then the slab itself is heated with four circuits of hydronic operated by two thermostats.

By comparison, the engineers who signed off on the Armory Park del Sol net zero development in Tucson discovered, as I did, that forced air isn't going to reheat a whole lot of concrete any time soon. But they didn't consider, as I did, that massive concrete without a equally massive heat recovery option raises energy bills and occupants' ire.

"Thermal mass is an energy benefit when passive solar design is applied to a home. However in production housing where passive solar design is often not feasible, a home having high
thermal mass may lead to additional heating energy use. The thermal mass may lead to occupant discomfort, and it also may consume a lot of energy to keep at a stable temperature for comfort. Depending on how the occupants use the thermostat (e.g., set back is often used), this massive structure may need to be charged frequently. "

http://www.solaripedia.com/files/166.pdf