Designing heating and cooling for a new build.

I read through this and a few things.that popped up.
Average Humidity levels will play a factor in the cooling system you choose. If your region is humid, radiant cooling is NOT for you, it will create damp conditions in spots often resulting in Black Mold which is really really bad.

Radiant Heating is seriously the BEST and most especially for Old Bones. That can be accomplished with Heat Pumps (Air or Ground Source) that can also provide you with standard Hot Water. High efficiency units are available and in the US qualify for IRA $ and you'd be surprised at what you can get from the IRA when it comes to heat pumps, heat pump water heaters (Ultra Efficient) and so on.

First Rule of Efficiency is Passive !
Preventing the summer heat and the winter cold from invading your house is just as important as keeping the heat/cool inside. Thermally Broken Walls & Roof Systems can and do resolve several of those issues right away. Thermally Broken structures prevent heat or cold from passing through the structural components. There are many ways to accomplish this and most do depend on the region/location. The most common method which has been used for millenia (yes you read that right) is to use an Air Thermal Break. This is also the most flexible and works in virtually all regions.
Roofs: A Cool Roof system as shown by @upnorthandpersonal is an excellent solution as it prevents heat transfer in/out of the house and actually keeps the attic / 2nd floor much cooler as a result.
CASE IN POINT: At the ridge vent in Mid Summer (35C outside) I see 55C Temps, at the peak of the Loft inside it is 25C while on the ground level of the main floor is 24C. The convection occurring pulls the hot out of the roof and it never gets inside. In winter the snow is kept 4cm (2") from the actual roof structure so no cold gets transferred. SEE ATTACHED PDF (Note company owner died from Covid, Company is gone but this is a really great explanation)
Walls: Thermally broken walls also prevent heat transfer between the building & the exterior. There are also several methods to accomplish this but for North America the most common is the "Rain Screen Siding" system that provides a 2"/4cm air space between the structure wall and exterior shell. When coupled to a Cool Roof system that utilizes natural Convection to move the air up to the Ridge Vents it keeps any humidity/damp away and the air break prevents heat transfer.

These TWO Systems CAN cut your heating & cooling costs IN HALF ! I use BOTH working in tandem. It reaches 105F outside and it is 77F inside with NO AC ! and that is with the windows open no less. In winter -35C/-31F my home is @ 25C/77F with a Frost Protected Slab Foundation and that only runs for 4 hours in a 24-hour period to maintain the heat.

The FPSF Foundation is the Kicker ! As the heat source in winter it is a marvelous regulator and everything in the home is warm ! Bed, Clothes, Furnishings etc... In Summer it IS the regulator as it's temp drops to 15C/60F so the slab keeps everything cooling as it cannot gain exterior heat. My FPSF Foundation does have 4" Thick HD-XPS foam under it and along the sides plus with 20" frost shield wings (I am in Algonquin Park Region) to prevent frost creep under the slab.

Insulation: My home uses only FOAMS but I used HD-XPS, EPS-II and PolyISO is "sheet" form as I built my walls in a modular fashion similar to SIPS. (Structural Insulated Panels). Spray foam (Commercial) was used only to seal in the sheet panels and to fill any gaps. The Foam Sheets I used are sadly not available in Retail Land. IE: My PolyISO sheets where 3.5 & 4.0" thick in 4'x8' sheets. My EPS-II foam (used in walls) is 5.5" thick an come in a 4'x4' T&G format. This material was sourced from Commercial Roofing Companies. NONE of it is "retail" and wait till you see what the price markup is to retail... You'll have a flip... up to a 500% difference ! I am NOT kidding !!! Retail = Gouged to death !

* Fiberglass Insulation is BAD ! Use Rockwool which is Hydrophobic, Pests/Rodents/Bugs HATE IT. it does not burn (it is rock wool afterall) has higher insulation value per inch and will not flop or compress like FGlass. Do seriously look at ROXUL if you will not be using Foams.
* Spray Foam: This is tricky. DIY kits exist but they not what many think. The cleanup after if not properly prepped can be a tremendously nasty mess. Some Foams used Soya & Other bio materials that turned out to be "critter attractants" and they are off market now (Thank Goodness). Most are now Synthetic Chemicals so as a result they will continue to offgas for a while, it can also be quite costly.

ERV/HRV is Critical else you will end up with a Sick House with moulds & mildews and worse.
Most systems nowadays do Heat Recovery during the air exchange. When you have a "Tight House" you must exchange air regularly to keep the indoor air quality. There are so many varieties that can do all sorts of things like dehumidify, pre-heat or pre-cool incoming air and more... Of course prices go accordingly BUT BEWARE ! Passive or Semi-Passive ERV's cost very little energy but Active systems with pre-conditioning and extra filtering can be Power Hogs too.

BTW: Heat Pump Water Heaters are finally hitting the North American Market en-masse. These are the Cat's Meow when it comes to energy-efficient hot water generation. I am getting a RHEEM 120V model. In USA, the IRA can pay for a good part of it too.

Also have a look here:

Hope it helps, Good Luck

OzSolar said:

I caught a podcast a few months ago that quoted a study that found high failure rates (well over 50% I believe) of HRV/ERV systems after years and the occupants were none the wiser that they had failed. The take away was that the house was in worse shape because it had been so tight to rely on HRV/ERV for indoor IAQ.

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That is a shame. The studies I have seen suggest that many systems were poorly designed and ineffective, and that ERV units did have a meaningful failure rate-- but most of the HRVs (recuperato, fans, and filters) were pretty reliable. (I am calling an ERV something that includes an enthalpy wheel; they have low reliability for sure).

There is a great market for handyman style HVAC techs to address components like this with regular maintenance. When operating properly the systems save a lot of money.

Humidity was my biggest fear. Humidity control seems to be more of an art than a science. I erred toward a less tightly sealed house rather than risk to much moisture being trapped in the walls. The geo thermal HVAC I picked was largely because it offered a variable speed compressor and fan, this is not common. Even high end HVAC generally only offer 2 speed compressors and fans. This allows the unit to run at low power and run long enough to dehumidify and still have capacity to move serious amounts of heat when needed. It turns on the fan 1st and ramps it up slowly, if this does not satisfy the temperature demand then the compressor comes on at low speed and ramps up slowly until the temperature requirement is met. There are several zones so heat exchange is targeted. The net results seems to be good temperature and humidity management.

There are a lot of existing housing that can benefit from reducing heating and cooling load so hope Danke doesn't mind asking questions along same lines..

upnorthandpersonal said:

This is why you don't typically use a vapor barrier with cellulose, but instead a vapor permeable barrier. For example, my roof:

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I need to fix my existing roof since it has serious heat loss (lots of ice dams) and was trying to come up with plan to use cellulose. It's cape cod style house which is notoriously bad at being able to properly insulate. Was thinking I would convert the attic into a conditioned space by building new roof on top of it. Install some ice/water shield across entire roof for the air barrier, cut off the short existing rafter tails and place new rafters on top of existing roof extending them out 2ft past roof edge.. fill between rafters with cellulose but then not sure details on top of that.

rhino said:

I need to fix my existing roof since it has serious heat loss (lots of ice dams) and was trying to come up with plan to use cellulose. It's cape cod style house which is notoriously bad at being able to properly insulate. Was thinking I would convert the attic into a conditioned space by building new roof on top of it. Install some ice/water shield across entire roof for the air barrier, cut off the short existing rafter tails and place new rafters on top of existing roof extending them out 2ft past roof edge.. fill between rafters with cellulose but then not sure details on top of that.

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You might do better with just rigid insulation over the existing sheathing and a vapor barrier over that, then run battens on top of that with another layer of sheathing, roofing felt, and shingles. If you want to "fix" the roof line then you can still do that, but maybe cantilever out rafter tails instead of full length. It eliminates the thermal bridging the new rafters would make, and you dont have the issue of the cellulose settling later.

Shimmy said:

That is a shame. The studies I have seen suggest that many systems were poorly designed and ineffective, and that ERV units did have a meaningful failure rate-- but most of the HRVs (recuperato, fans, and filters) were pretty reliable. (I am calling an ERV something that includes an enthalpy wheel; they have low reliability for sure).

There is a great market for handyman style HVAC techs to address components like this with regular maintenance. When operating properly the systems save a lot of money.

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If they were specific as HRV vs. ERV I didn't catch it but thanks for adding those details.

It is a shame but it goes along with something I've noticed after being around "this stuff" for a long time. "perfect is the enemy of good enough"

The elephant in the room that we aren't talking about but have hinted at which is:

Squeezing that last bit of out of anything (not just HVAC efficiency) not only adds expense but in many cases requires maintenance that most don't do, reduces reliability and increases repair costs.

OzSolar said:

Squeezing that last bit of out of anything (not just HVAC efficiency) not only adds expense but in many cases requires maintenance that most don't do, reduces reliability has increased repair costs.

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While not universal, there are some other benefits that a tight house with managed ventilation air have-- like a commercial building. Dust and pollen control, temperature stability, managing vapor movement, etc. The level of benefits are tied to climate zone, but you also have things like fires and smoke like the northeast saw this week where maintaining indoor air quality is much easier.

OzSolar said:

Squeezing that last bit of out of anything (not just HVAC efficiency) not only adds expense but in many cases requires maintenance that most don't do, reduces reliability has increased repair costs.

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Quite correct and this is where people that step away from Passive Methods to Active Methods (using equipment & tech) hit a wall. A great deal can be accomplished using passive methods.

A good example, look at building pre-1925 pretty in most parts of the world. You will see Transom Windows/Panels between rooms to allow airflow. You will see double-hung windows with screened vents at the top & bottom. You see Cuppolla's and similar on roofs for passive venting (that gave way to turbines etc). Also did anyone ever "click" on why many old style double hung windows had an angled baffle (often glass but not always) at the bottom ? So you could keep the windows open even during heavy rains, it would direct the air up and catch any rain that came in and shed it back out. It also kept direct breezes from affecting the inside. This was most common in commercial buildings but many homes had it too.

Many methods used in the past before "Technological" solutions came to exist all still work today. If implemented properly, it can take care of the Lion's share of the load, leaving the Technical solutions to a much lighter load. Look at how many have forgotten the use of Shade Trees to keep the home out of Direct Sunlight.... Or using trees/shrubs for Windbreaks to keep direct winds from hitting the home. Funny how some actually think that is a heresy ! Using trees to shade the house OMG !!!

I learned about these methods and more by renovating homes built pre-1900 and also due to my love of history & archeology (which is what takes me back to millennia-old methods).

Pacific, Equatorial, and even Mediterranean homes also often had Louvered Doors as opposed to solid ones so they could provide visual privacy but still allow air to flow throughout the structure. Anyone who's traveled to far-flung places may just recognize this.

Many Methods can be used anywhere in the world, regardless of where & when it was conceived.

If I were building a new home, I would go with LG Multisplit for heating and cooling, closed cell foam in the exterior walls and floor joists between levels, sound rock in interior walls, and no geothermal. A simple solar setup is cheaper and will cover all your energy needs.

I also like hybrid water heaters, and they work well with central AC units during the summer, so that is an option as well.

Another thing that many people overlook is windows. Suspended film windows are far more efficient, and is worth the look, so I would weigh their costs as well.

Odom1957 said:

If I were building a new home, I would go with LG Multisplit for heating and cooling, closed cell foam in the exterior walls and floor joists between levels, sound rock in interior walls, and no geothermal. A simple solar setup is cheaper and will cover all your energy needs.

I also like hybrid water heaters, and they work well with central AC units during the summer, so that is an option as well.

Another thing that many people overlook is windows. Suspended film windows are far more efficient, and is worth the look, so I would weigh their costs as well.

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Why LG?

Danke said:

Why LG?

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LG has branch ducts on their smaller ceiling cassette units, so you can run vents to closets and bathrooms, and allow more units per condenser than most of the other brands.

The only brand that beats LG is Mitsubishi, and those things might as well be made of platinum, because they are EXPENSIVE.

Daikin is another great brand, but there are some limitations with indoor unit sizes and features that LG offers, like the Branch Duct.

If you only plan on a few indoor units, then more brands open up at a decent price point, but all require every single line set to return to the condenser separately.

Branch Box systems are much better than individual lineset systems.

Odom1957 said:

LG has branch ducts on their smaller ceiling cassette units, so you can run vents to closets and bathrooms, and allow more units per condenser than most of the other brands.

The only brand that beats LG is Mitsubishi, and those things might as well be made of platinum, because they are EXPENSIVE.

Daikin is another great brand, but there are some limitations with indoor unit sizes and features that LG offers, like the Branch Duct.

If you only plan on a few indoor units, then more brands open up at a decent price point, but all require every single line set to return to the condenser separately.

Branch Box systems are much better than individual lineset systems.

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When i was installing my AC a triple branch unit was much expensive than 3 single ones! but not sure wich brand it was.

mrdavvv said:

When i was installing my AC a triple branch unit was much expensive than 3 single ones! but not sure wich brand it was.

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Yes, it seems like air handlers are expensive. Might as well buy individual units that include an air handler.

This is false information. An evaporator doesn't cost more than a whole system.

Odom1957 said:

This is false information. An evaporator doesn't cost more than a whole system.

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Who said that?

My old LGs were CRAP compared to my Mitsubishi, not to mention 30dba less noise...
Mitsubishi Zen is really worth the money IMO.

House shaped close to a cylinder as possible. Min. exterior area/max vol. Taped seam Polyiso exterior. (how I built my house back in 1989.) Don't use spray foam anywhere except to fill in 1/4"or so gap around sheets of Polyiso intentionally cut too small. Large room in center of cylinder house to act as a plenum. Populate center room with single zone wall mount mini-splits . Different model mini-splits to work at highest efficiency at different ambient temperatures. Only run the most efficient mini-split(s) from group. Jump ducts connected from main center room to rooms located around the center room. Individual rooms with their own thermostat that turn on/off DC fans to draw air from center plenum room. Insulation in walls between all rooms. If heat exchanger are required DIY maybe try using Ebay turbo Intercoolers. Minimum windows but enough to meet ingress/egress codes. Thermal solar on room/greenhouse on south side of home. with IBC totes, 55 gal. barrels etc. for heat storage. Foam sheet insulation under all floors.