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Thermally ideal, concrete animal shelter design 2

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dropgoodbricks

dropgoodbricks

Student
Oct 12, 2023
6
I have a Master's in IT and took some physics courses, but I'm not yet at the level where I could model a thermally ideal concrete structure for animals in northern US winters, so I'm hoping to get some advice here. I have access to chief architect software if anyone wants to just whip up a quick and dirty design that I could open in that software.

I'm planing to build something like a 4ft x 8ft animal shelter out of cinder blocks with a concrete, rebar filled footer about 16 inches below grade on wet clay. I'm trying to use the thermal mass of the concrete to keep the animals warm as well as possibly add interior insulation. I was thinking about putting 2 inch R-10 solid foam board between the slab and vapor barrier and 3/4 clean stone foundation as well as using the same insulation along the interior walls. To prevent the animals from destroying that foam board, I was going to cover the walls with plywood. The roof will likely be a typical wooden triangle style with 29-gauge sheet metal and I may put some insulation up there as well. I'm hoping someone can help me make this ideal and not just my best guess from my own research. I want to learn to do it right, not just "build something".
Here are some questions I have:
1. Is there a better option for the interior wall insulation than I described above?
2. What would be recommended for ventilation that wouldn't make it too cold?
3. I'd like to have one side with a small animal door and the other side have a larger door for humans to access the interior. What would be a good solution for the human door that would be cost effective and not reduce the insulation any more than necessary? I was thinking a roll-up style with some insulation board on it might work so there is no swing reducing space or pushing out into snow drifts.
4. Is there an electrical alternative to PEX floor heating so I don't have to worry about freezing water?
5. Is there a clever way to run water to this building without it freezing in the pipe along the way? I suppose I could run a water pipe under the frost depth of 42 inches, but maybe there is a better way?
6. Should I run electrical with the water pipe and cast a schedule 40 2in PVC pipe into one of the walls when pouring the concrete or is there a better way?
7. Can anyone recommend any further changes or modifications to improve this?

Note: I currently have a skid steer rented and could earth berm much of the sides, but how thick would that need to be for it to be effective and will poured concrete into cinder blocks with rebar be enough to handle the additional weight of that or do I need further structural enhancements such as something like a retaining wall of, for example, railroad ties held in place by metal pipes filled with concrete?
Note-2: I could do the earth berm with clay or sand. Is there a benefit to doing one or the other?
 
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Unless the animal occupying this is huge, 4'x8' is way too big. The primary way the shelter will stay warm is by retaining the animal's body heat within the structure (and bedding), so making the shelter just big enough for your animal to get in and bed down is ideal. Thermal mass of block or concrete will help, especially if you can incorporate a south-facing door that is left open during the day, or a south-facing window with insulated shutters, than can be open during the day and closed at night. Solar heat gain retained by walls and floor that have a high thermal mass will go a long way towards making the shelter comfy.
 
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Yes, there is electric floor heating that is used under tile. We installed a bunch in a previous house. Think there is a company called Easy Warm Floor. And others.

Water is going to be an issue. Yes you can run it deep, then up inside the building. Don’t put it in the walls. Get a long frost free type hose spigot that goes into the ground (so the valve is buried).

There are insulated metal doors for houses that should work.

Good luck keeping the unwanted critters out!
 
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And the thermal mass is only going to help if you can first get it warm. Once it gets cold its going to work the opposite.

What kind of animal is this for?
 
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Great tips so far, thanks!
The shelter is for multiple dogs, 4 large breed ones at the moment. In the future it may be for less hardy animals.
Yes, for 1 dog it would be a bit large, but we had them in an enclosure of similar size in warmer seasons and the size seems about right to prevent fighting but allow huddling. It also matches what some dog house manufacturers scale to.

Heat will be added in some way, preferably electrical to augment what the animals produce on their own, but we need to make sure the dogs don't destroy the heater. Easy warm floor sounds like a good option, I'll check into that.

The idea so far is to try and earth berm it as well using some sand on the other side of the walls. This will serve as a wind block as well as get the outside temperature towards about 45 F in winter and 55 F in summer, so we're not trying to heat up from freezing, but rather from the temperature underground. If the frost depth for the area is 42 inches, does that mean 42 inches of sand starting from grade and going up would potentially freeze? Theoretically speaking, if I had a pile of sand 8 ft above grade, would the top 42 inches be potentially frozen and the remaining 4-ish feet be warmer or would anything above grade freeze, regardless of how high I pile it?

I'm not sure how the frost line will make a difference or how much sand we'll need for it to "heat-sink" to the temperature below frost depth (45 - 55 F).
So I'm looking for advice on how to take a starting point of about 45 F and warm that up a bit by isolating the heat the dogs produce and the heat a heater of some sort produces.

Can anyone recommend insulation options better than 2 inches of XPS foam board insulation behind plywood to keep it safe from the dogs? It's the R-10 Pink Panther stuff.

Also, what if I built it a little larger and had a wooden dog house inside it? That would air-gap things a bit but I'm afraid the heat from the dogs wouldn't use the thermal mass well, however one dog owner does it like this and is happy with the result.

Does anyone know how they build / do insulation in extremely cold places like Alaska or towards the poles? I don't mean snow igloos, but something from normal building materials.
 
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The frost depth would be from the surface of the ground, wherever it ends up after grading, not that you need to worry about frost heave if you have a foot or more of sand under the foundation/slab.
 
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Frankly, if its 45F inside, out of the wind and rain, the dogs should be just fine. Give them some pads, blankets, dog beds to sleep on.
 
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Something like this does not have to be all that fancy.
When we had our first pair of Labrador retrievers, I built doghouses for each (location, northern Ontario Canada). Typical temperature range: +34 C max in summer to -40 C min in winter. One house per animal: rectangular with a sloped roof. Construction was simple 0.75 inch thick plywood, with an ordinary shingled roof. Floor was lifted above ground by a set of 4 inch x 4 inch posts lying on their side and acting as a foundation support. This did two things: kept the moisture off the plywood flooring and developed an air barrier under the structure to limit heat siphoning during the winter.

Structure was designed as two "rooms": a vestibule with the exterior door that faced south, and a "sleeping area" whose entry faced west into the vestibule (and located at the opposite end of the vestibule from the exterior door). South facing wall was 32 inch height; north facing wall was 40 inch height. Floor (of the whole structure) was roughly rectangular, at nominal 40 inch north-south and 60 inch east-west. Vestibule and sleeping area were relatively equal size (30 wide x 40 length), with a separating wall that was a uniform 32 inch height (same as shortest wall) - end post ran from flooring to roof slope to support the wall end and define entryway between the two areas. exterior door had a simple flap made from two pieces of carpet fastened back to back (so the "weave" of the carpet showed in both directions. This was a result of experimentation - we found the weave did a better job shedding rain and snow than the backing material.

In the winter, we laid down a bed of straw roughly 3 inch thick over both vestibule and sleeping area to provide additional insulation. Straw was removed during summer months to prevent "critters" moving in.

The low slope of the roof provided another surface for the dogs when they wanted to just laze about on a sunny day (winter or summer!). The dark colored shingles retained/radiated heat surprisingly well, even in mid-January.

Converting energy to motion for more than half a century
 
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What Gr8blu did sounds like a really good idea. I'll incorporate some of that into my design.
I know I could build this much more simply and quickly out of wood, mostly like Gr8blu did.
However I'm using this project to learn about house foundations and to find the best practices for them, but on a small, cost-efficient scale. This is a learning project as a reality check so it's not just ideas and drawings on paper. It's not just a dog house but more of a scaled model of how I'd build a real house foundation. Please just pretend this is a tiny house when answering.

The yard is very wet clay and it becomes a wet fudge in spring and fall, cannot be driven on, and freezes solid in winter under a foot or two of snow with around -20 F as the coldest sustained temp, but we also see upper 90's to an occasional 100 F in the summer with high humidity. So I'm really looking to learn all I can about using thermal mass to phase-shift the temperature in there, like a European castle wall does, (1 yard thick sandstone makes those castle walls day temp at night and night temp during the day). I'd like to earth berm this as well so it's built into a hill I make for even more thermal mass. The earth berm would also be a way to test my engineering if I build a cellar like that later to store food that can't freeze.

However I may skip the earth berm if it's not sound engineering for what I'm trying to do (please advise). I'm more concerned about the winter being warm enough but I would like to see it at say 60 F or cooler in the summer so the dogs can cool off without going under the house deck or into the ponds.

Some further questions:
01. If the rest of the area is clay stew, can I just dump a foot of sand in there and then stack rocks, insulation, vapor barrier, concrete slab on top of that sand, or will that sand slowly dissolve into the clay / flow out with the drainage and make the foundation have gaps and become unstable? Should I put a Geotech fabric on top of the sand / under the rocks? Should the sand be wrapped in geotech fabric so it doesn't wash away or will that not help?

02. What kind of rebar should I be using for the wall footing horizontally? I've heard of people using old fencing like cattle-panel but I wanted to get the proper rebar for the project. What rebar should the walls have? What horizontal rebar should the slab have? I've heard non-reinforced concrete makes 4000-psi concrete only good for about 40psi. Not that the dogs are heavy, but it's a scale model of a house.

03. How best could I do drainage away from the foundation to prevent water from collecting under it. Our garage had massive issues with that until we ran long drainage tile from there to the pond (about 200ft) and then it dried right up. What is the PROPER way to do this (if it were a house)?

04. I was looking at 6AA 3/4-in clean stone for the foundation (possibly on top of the sand if sand is ok to use in wet clay). Is that ideal or is something better? I don't want anything with clay or sand mixed in, as I have tons of both on the property. I just need rocks.

05. Would painting it black be a good idea to absorb more energy from the sun when it's not under snow?

06. Do I need to add say some 4-in or 6-in PVC pipes for ventilation? I'll likely use the hung carpet for doors like Gr8blu did but what about mold issues due to poor ventilation or even on the carpet itself? I'm trying to figure out how to keep it dry in there because Golden Retrievers love to swim...

07. I'm considering adding some plexiglass on the roof for skylights so it's not dark in there. I've also seen videos of people in Africa using old "white" / clear glass bottles that are epoxied together for skylights. What else would work better and not be very expensive? Any other recommendations?

08. Straw on the inside for bedding seems fine and I'll just sweep that out as needed to clean it. Would there be any problem "sealing" the concrete floor with a concrete sealer / paint so no fluids or nasties seep into the concrete? Could that cause issues with mold or the concrete's ability to absorb and give off water? I know with sandstone it can cause mold issues but I don't know about concrete or if sealing it too much could cause it to crack.

09. What else could I do to keep the natural temp somewhere between say above 45 F in the winter and 60-65F or colder in the summer?

By the way, I'm modeling some Youtuber's channel called "Mason Dixon Acres" for the foundation design.
If anyone's interested, it's these videos that are relevant for foundation work:












Thanks for the replies!!
 
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Thanks SWComposites! I've seen that site before but I haven't looked at it recently in light of this project. One thing I'm looking for is some of the math / formulas behind earth berm structures. I understand the R-Value math and I think I understand the U-Value math. However I'm still not sure on some things like these and the practical application of those formulas:

1. How thick must the earth berm be in order to be the same temperature as grade would be or below frost-line grade?
For example if I had a hill that was say a yard thick on either side as well as on top, how would that differ mathematically from a foot thick or 2 yards thick earth berm?

2. What material would be best for earth berms? I'm thinking sand with topsoil and grass roots holding it in place would work well because it won't heave and ho like wet clay does when it freezes but I think adding rocks in there would be a better mix for thermal mass. Is there a best practice for this?

3. Say a dog's body is 102 F and it radiates X BTU. How much heat is lost if the enclosure is significantly larger than the dog? Say there is 1 foot of space on all sides of the dog. What's the math that shows the loss to that air? What if it were 2 feet or x feet?

4. How does that dog's heat warm up the concrete walls / earth berm in a meaningful way, mathematically speaking? I think what I'm not yet sure about is how a dog's heat will warm up the walls if they are in a heatsink (yeah, I'm a computer guy) with an earth berm or the grade?
I'd assume it would just sink to the temperature of those objects just like grounding out a circuit to earth removes the wattage it's carrying. However, if the transfer were slow enough, maybe the dog could heat up say an inch or two of the interior of the concrete walls, enough to make it warmer than the loss of heatsinking to ground. In my head I see the thermal mass more like a resistor in an electrical circuit that slowly prevents the amperage from draining as fast as it otherwise would, but I can't imagine all of this well enough to do any calculations.

Can someone please throw some formulas at me with brief explanations that I could use to figure out what the interior temperature of the occupied structure would likely be? I learned long ago in physics to stop trying to trust my intuition and to just use proven formulas...

I'll go read up on that site and stop asking questions it might answer, but if the answers are simple I'd be delighted to read a quick reply with those answers here.
 
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Its not just formulas that you need (and its WAY too long since I took thermo and heat transfer classes for me to be useful) but you also need a bunch of material properties which may be hard to pin down.
 
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There are text books out there on passive home design which might help. Its all about energy storage and passive heat gain/loss.
 
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Thanks SWComposites for the replies. A textbook recommendation would be fine. I'm sure the formulas would be in there.
Do you mean something like this?
To be clear on my scope of the project, while I'd like to learn more, I think full on passive home design is going to be too much of a deep dive at the moment. I can build that knowledge over time and possibly take classes, but in the end, I need a dog house before winter and must reduce project scope to that for now. I'd like to model a house as best I can, but I'll limit that to the proper scope.

Having taking those classes, could you ballpark something, even very roughly?

I'm thinking for the interior:
Plywood, R-10 2-inch pink board insulation, and then the concrete block should be a good enough mix of insulation and thermal mass with maybe some earth berm sand stacked behind that. Can you comment on that or suggest something better?

My reasoning for the insulation above:
Plywood will absorb moisture and give it back off to buffer humidity better than concrete alone would. It will also protect the pink insulation board from the dogs. The insulation board should really slow heat transfer away from the dogs quite well. Any heat that does transfer through the insulation board will go into the concrete block, and buffer there as well, due to the thermal mass. Beyond that, the other side of the concrete block should be the below grade kind of temperatures of somewhere between 45 F and 55 F, so worst case, if I'm completely wrong on my design, it still won't be freezing in there.

I also just read here, that one of the original designs of an earth berm has a vapor barrier all around the building like an umbrella, which might make sense as well, to ensure it stays dry:

I'm however still not sure on this point:
If the frost depth here is 42 inches, would I need say 43 inches or more to achieve temperatures above freezing due to the earth berm or would I achieve the usual 45 F temperature that's found below frost depth with less dirt/sand on top of the structure / on the sides of the structure?

Does any software exist to calculate some of these things / answer some of these questions? Maybe I could play with that a bit. I'm slowly figuring out the "Chief Architect" software at the moment but I've not seen any functionality like that yet. I can get a student license for most anything if needed.

I'm not going to bother with any kind of interior framing with the fiberglass insulation or anything like that. I'm also fine with adding an electric heater caged away from the dogs if I can't do any better with passive tech than what I described above.
 
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Side note: Am I posting this in the right forum or are there more appropriate forums for this or other websites you guys know of that might be able to provide additional help? I'll share the information I figure out back and forth for everyone's benefit. Any suggestions would be most welcome.
 
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