Design class: BudgetValidation status: Data validated
Tote-in-Tote + Straw
The Alley Cat Allies method: a large tote of about 30 gallons, a foam slab on the bottom, a smaller tote of about 20 gallons inside and straw, with one entrance through both.
A warm shelter that gets damp can be worse than a simpler one that stays dry.
“Data validated” means only the data and calculations are checked; the model has not been built or tested physically.
Capacity1–2
Outside size760 × 470
BuildBeginner
Time (estimate)45 min–90 min
model v1.0.0compiler P1.0.0plan ed94155d1237a1b1Plastic toteWinter · Rain
This model has no 3D view; the drawing and dimensions below fully describe the construction.
EPS foam board1 sheetssheet nesting · 1 × 1000 × 500 mm (planning format; check with your supplier).
Plastic storage tote2 pcsfrom geometry · Outer and inner tote; the inner one must fit with clearance.
Heavy-duty tape1 packassumption · Cover the sharp edges of the cut opening from the outside.
Bricks5 pcsassumption · Four stable supports under the corners.
Straw1 baleassumption · Loosely to a quarter or half of the height; keep the rest dry for refills.
Cut list
Parts to cut
IDPartDimensionsQty
slab-floorSlab under the inner tote · EPS foam board760 × 470 × 30 mm1
Sheet nesting
Parts on sheets
Sheet formats are planning assumptions; check your supplier's format. Sloped parts occupy their rectangular envelope.
EPS foam board · 30 mm1 × 1000 × 500 mm
Sheet 1 · 71% used
Layers and thermal
Known and unknown layers
Partial estimate: some layers are unknown, so no U-value is calculated. Only the resistance of known layers is shown.
Wall
Plastic storage tote · 3 mm (assumed)unknown
Plastic storage tote · 3 mm (assumed)unknown
Known-layer resistance: 0.00 m²K/W
Floor
EPS foam board · 30 mmR 0.79
Plastic storage tote · 3 mm (assumed)unknown
Plastic storage tote · 3 mm (assumed)unknown
Known-layer resistance: 0.79 m²K/W
Not included
Air leakage through the entrance and joints
Thermal bridges through battens, edges and fasteners
Moisture, condensation and property changes of damp material
Heat produced by the animal
Wind and transient temperature changes
Assumptions
Thin layers without a sourced λ (roof covering, film, mat) are not counted.
The tote wall has no sourced λ and remains an unknown layer.
Tote dimensions are a nominal envelope; measure yours.
The estimate is not a temperature guarantee and does not claim the shelter is safe to any temperature.
Water and moisture
Weather exposure
A warm shelter that gets damp can be worse than a simpler one that stays dry. This is an explanation, not a condensation calculation.
✓Ground contactRaised about 100 mm off the ground.
✓Rain splashHigh enough that rain splash from the ground does not hit the floor.
!Roof drainageThe lid is flat: water runs off to the sides. It must close well and the entrance must not sit below a drip edge.
✓Rain at the entranceThe entrance sill is 80 mm above the floor.
✓DryingCan be opened to dry out and change bedding.
✓Absorbent materialInterior surfaces do not absorb much moisture.
✓Maintenance accessAccess for checks and cleaning is simple.
Local price profile
Cost estimate
Quantities come from the model. Prices are not fabricated: enter what you actually pay locally and the estimate stays in your browser.
Prices entered: 0 / 5
EPS foam board1 × 1000 × 500 mm (planning format; check with your supplier).
1 sheetRSD 0
Plastic storage toteOuter and inner tote; the inner one must fit with clearance.
2 itemsRSD 0
Heavy-duty tapeCover the sharp edges of the cut opening from the outside.
1 itemRSD 0
BricksFour stable supports under the corners.
5 itemsRSD 0
StrawLoosely to a quarter or half of the height; keep the rest dry for refills.
1 itemRSD 0
Estimate from entered pricesRSD 0
Sheet, XPS, framing and hardware quantities come from the compiler. The estimate still excludes delivery, tools, labor, local taxes and unforeseen losses beyond the stated allowances. PROVISIONAL and product-specific items remain explicitly labeled.
Placement
Check the spot
No obvious issue detected
This is not a safety certificate for the spot: it only means none of the listed questions is ticked.
Bedding
What goes inside
RecommendedStrawRepels moisture and stays loose. Replace when damp, compacted or soiled, and when seasons change.
Not recommendedHaySoaks up moisture, turns cold and can mould. If already in a shelter, replace it with straw.
Not recommendedBlanketAbsorbs and holds moisture; a damp blanket chills. Wash and swap as soon as it is damp.
Not recommendedTowelAbsorbs moisture like a blanket. Wash and swap as soon as it is damp.
Not recommendedWood shavingsPartly absorbs moisture. Change when damp or compacted.
Not recommendedWashable dog bedDepends on fabric; textile absorbs moisture. Dry or swap as soon as it is damp.
Not recommendedNo beddingNothing to absorb moisture. Not applicable.
Maintenance
Inspection schedule
WeeklyCheck that the straw is dry and loose; replace it when damp or compacted.
WeeklyCheck for water or dampness on the floor and walls, especially under the entrance.
After stormsAfter rain or snow check the interior and the ground under the shelter.
WeeklyCheck for scratching or chewing of the foam; protect or replace damaged parts.
MonthlyCheck the plastic for cracks and sharp edges around the opening.
Each seasonQualitative: plastic and foam become brittle in sunlight; replace them when they fade or crumble.
WeeklyCheck that the lightweight shelter is still weighted or secured.
After stormsClear snow from entrances and exits so the animal cannot be snowed in.
Each seasonClean the interior; service access must allow cleaning without dismantling.
Upgrade path
Where to go next
Each step states what you add, what you gain and what stays limited. A new model has a new plan ID; changing an existing build has no canonical plan.
A more complete insulation layer around the inner tote.
Still limited
Plastic cracks over time; not a durable timber build.
New material
EPS foam board
Don't have this material?
EPS foam board · 30 mm
XPS foam boardabout the same layer resistance at 27 mm (conservatively 30 mm); thermal equivalence is not structural
PIR / polyiso boardabout the same layer resistance at 19 mm; thermal equivalence is not structural
Cork boardPossible substitute requiring redesign: at least one material has no sourced thermal conductivity, so an equivalent thickness cannot be calculated.
Plastic storage tote
EPS shipping boxThe substitute changes the construction (thickness, strength or water protection); parts and joints must be re-planned.
Old pet carrierThe substitute changes the construction (thickness, strength or water protection); parts and joints must be re-planned.
Progress is stored in this browser against the exact plan ID; it works offline once the page has been opened.
0 / 6steps completed
Foam slab on the bottom
Lay a foam slab in the bottom of the large tote and set the small tote on it, leaving a gap on every side.
Cut the entrance
Cut a 150 mm × 150 mm opening through both totes, aligned, with the sill 80 mm above the floor so rain and snow stay out. Face the entrance away from the prevailing wind. Cover or sand sharp edges.
Close and weight it
Close the lid and put a brick or stone on it. A light tote must be secured against wind.
Raise the shelter off the ground
Set the shelter on four stable bricks, about 100 mm above the ground, so the floor does not touch cold, wet ground. Check that it does not rock.
Add straw, not hay
Loosely fill straw to a quarter or half of the interior height. Do not use hay, towels or blankets in an outdoor winter shelter: they absorb moisture and chill.
Choose the spot and secure it
Set it against a wall or fence, out of the wind, away from roof runoff and roaming dogs. Weight or secure lightweight shelters. Check the spot with the placement checklist.
Provenance
Sources and verification status
A source supports a guideline or material value, but it does not confirm this specific model. Container sizes are assumptions and build time is a planning estimate.