Contents
House specification (the standard every house is built to)
Status: concept targets, 27 Sep 2026, revised 21 Oct 2026 for the operating model (the estate owns and maintains every house, operating-model.md) and the shared utilities (utilities.md); revised 3 Nov 2026 for the Type C corner house (§6b). Numbers are design targets to be confirmed by the energy model, structural engineer and vendor quotes. Costs for each item are in costs-and-rent.md. Bracketed numbers such as [5] refer to sources.md.
The rule: one spec for every house in the estate. Tenants choose Type A, Type B or, at the four corners, Type C, never a cheaper envelope.
0. Built to be owned for 50 years
The estate keeps every house and pays for every repair, so the spec optimises the cost of owning the house for decades, not the cost of handing it over.
| Principle | What it means |
|---|---|
| Design life | Structure 50 years or more; roof, walls and windows 30 years or more before major renewal; systems replaced on a planned cycle (component reserve in the model) |
| The best envelope we can verify | Passive House level airtightness, n50 ≤ 0.6 /h, the limit the Passive House Institute requires;[41] every house modelled in PHPP (one model per house type and orientation) and certified by an accredited certifier |
| One model per system | One approved AC model family, one ERV, one inverter, one heat pump water heater, one window system and one set of ironmongery across the estate, with spares in the estate store |
| Maintainable | Every service reachable without opening a finished wall: plant room outside the envelope, service ducts, access panels, no concealed joints; PV with walkways and anchor points |
| Durable materials | Stainless steel grade 316 fixings outdoors, powder-coated aluminium, through-coloured render with silicone paint, porcelain tiles, no gypsum board in wet rooms |
| Measured | Meters and sensors on every system, so faults show on the estate dashboard before the tenant has to call |
| Efficient in use | Appliances in the highest Thai energy-label class, induction hob, heat pump dryer, LED lighting, DC ceiling fans so AC set points can sit higher |
1. Site and structure
| Item | Spec | Why |
|---|---|---|
| Flood | Estate filled so finished floor level is at least 0.5 m above the highest recorded local flood level, plinth +0.60 m above road | Oct 2024 floods[19] |
| Seismic | Designed to the 2021 ministerial regulation for Zone 3 (Chiang Mai),[24] ductile detailing at joints | Chiang Mai is Zone 3 |
| Structure | RC frame, post-tensioned or hollow-core first floor, soil test per plot row | Standard, but engineered |
| Termites | Physical barrier (mesh or graded stone) at slab and penetrations, no soil poison as primary | Long life, tenants with children |
2. Envelope
| Item | Spec | Target |
|---|---|---|
| External walls | AAC 200 mm + 75 to 100 mm external insulation (mineral wool or EPS ETICS), render, no bridges at slab edges | U ≤ 0.35 W/m²K |
| Roof | Metal standing seam, high-reflectance coating, radiant-barrier sarking, ventilated attic, 150 mm mineral wool on an airtight ceiling | U ≤ 0.20 W/m²K, SRI ≥ 80 |
| Shading | 1.2 m eaves all round, 1.5 to 2.5 m pergola on the garden side, external louvres on E, W and upper S windows | No direct sun on glass 10:00 to 16:00 from March to October |
| Windows | Thermally broken aluminium or reinforced uPVC, double glazed Low-E, inner pane laminated, multipoint locks, fixed insect screens on every opening sash | Uw ≤ 1.8, SHGC ≤ 0.30 |
| External doors | Insulated core, 3-point lock, full perimeter gaskets, threshold seal | Airtight, security class RC2 equivalent |
| Airtightness | Continuous air barrier drawn on every section; tapes and grommets at every penetration; blower-door test at pre-plaster, at handover and at every change of tenant | n50 ≤ 0.6 /h (Passive House limit[41]) |
| Floor | Slab edge and perimeter insulation 50 mm, vapour barrier | No condensation, no rising damp |
Reasoning: in Chiang Mai the envelope's job is to keep heat and smoke out, not to keep heat in. Shading plus roof insulation cut most of the cooling load; airtightness is what makes the ERV filter the air instead of the gaps around the windows.
3. Air: ventilation, filtration, cooling
| Item | Spec |
|---|---|
| Fresh air | Ducted ERV (enthalpy core, it also moves moisture), about 0.4 air changes/h, supply to bedrooms and living, extract from baths and kitchen |
| Filtration | F7 (ePM1 55 %) pre-filter + H13 HEPA on supply, filters changed by the estate team from outside the house (plant room); filter pressure drop monitored |
| Smoke mode | Supply 10 to 15 % above extract to hold the house at slight overpressure when outdoor PM2.5 is high; switched automatically from the outdoor sensor |
| Cooling | Premium inverter split units (SEER ≥ 20), one approved model family, one per bedroom + living, sized from the energy model (not "1,000 BTU per m²"), dehumidify mode, concealed pipework in sleeves, local control and fault codes through ESP32-Faikin |
| Fans | DC ceiling fan in every bedroom and the living room |
| Kitchen | Recirculating hood with grease + carbon filters, or ducted hood with motorised damper and make-up air interlock |
| Sensors | PM2.5, CO₂, temperature, humidity in every bedroom and living, outdoor station per estate |
4. Energy
| Item | Spec |
|---|---|
| PV | 6 kWp on the south roof slope at opening, tier-1 modules, string inverter in the plant room; roof structure, rails, penetrations and DC conduit for 10 kWp, filled when PEA confirms export (utilities.md) |
| Grid | Connected to the estate's private low-voltage grid, not directly to PEA; PV surplus feeds the neighbours, the water plant and the common loads |
| Storage and backup | No home battery. The estate's central battery (170 kWh in the 14-house flagship) backs up the whole house when PEA fails, and the estate's 200 kVA standby generator recharges it in a long outage; EV charger and water heater are shed first |
| Hot water | Heat pump water heater 200 to 300 L with recirculation loop, run in solar hours by the estate's energy management system |
| EV | 7 kW charger in the garage, metered, load-managed by the estate's energy management system |
| Metering | Revenue-grade electricity sub-meter at the house connection (allowance and billing), per-circuit metering inside, data in the local Home Assistant and on the estate dashboard |
5. Electrical installation
Per B4L construction-standards
standards/electrical/:
- Tier-1 protection gear only (ABB, Schneider, Siemens), bought through authorised distributors because counterfeits of these brands are common in Thailand.
- House supply from the estate low-voltage ring through a feeder pillar and the house sub-meter.
- RCBO (30 mA) per final circuit, not one RCD per board.
- Earthing designed with the estate's own transformer (earthing system fixed by the electrical engineer), local earth electrode ≤ 5 Ω at each house, main equipotential bonding.
- Type 1 + 2 surge protection at the estate main board and at each house board, Type 2 at sub-boards and the PV DC side.
- Everything in conduit, no buried cable without conduit, spare conduits to every room.
- Full test and inspection record per house (insulation resistance, loop impedance, RCD trip times), handed to the tenant file.
- Data: fibre to every house, Cat6A to every room, Wi-Fi access points in ceilings.
6. Plumbing
Per B4L construction-standards standards/plumbing/:
- PEX-AL-PEX press-fit system (Pimaflex / Uponor / Geberit class), manifold distribution, no compression fittings, no concealed joints.
- Silent drainage stacks (≤ 20 dB class).
- Supply from the estate water plant (treated and chlorinated) by gravity from the water tower, about 2 bar at the street, through a smart water meter, check valve, filter and an automatic leak shut-off valve in the plant room. No tank, pump or whole-house treatment in the house.
- Leak sensors under every sink, at the water heater and in the plant room, closing the shut-off valve.
- Garden irrigation from the estate's non-potable line (treated effluent and a covered rainwater cistern; there is no open water on the estate).
- Pressure test and leak record per house.
6a. Attached garage
Every house is two storeys with a two-car garage attached on the street side (Type C: three cars, §6b). The garage is a single-storey, unconditioned room outside the airtight and insulated envelope; the house wall it shares is built as an external wall.
| Item | Spec | Why |
|---|---|---|
| Size | 6.5 × 6.0 m inside, two cars side by side, storage wall and bicycle rack at the back; not counted in the 180 m² (Type B 240 m²) | Two cars without squeezing past; space for the things a garden house collects |
| Structure and roof | RC frame and masonry like the house; flat insulated RC roof with membrane, rails and conduit so it can carry PV later | Shades the street-side wall; extra roof area if PEA allows export |
| Door to the street | Insulated sectional door about 6 × 2.5 m, motor with battery-backed control, photocells, manual release, opened by remote or the tenant's app; open/closed status on the house dashboard | Quiet, durable, one model across the estate; the estate team sees a door left open at night |
| Door to the house | Fire-rated (30 min), self-closing, gasketed and airtight, with threshold seal, into the laundry | Keeps car fumes out of the house and stops the garage breaking the n50 ≤ 0.6 test |
| Air | Permanent high and low vents to outside; ERV fresh-air intake on the garden side or roof, at least 3 m from the garage door | No fumes or petrol vapour into the ERV; the garage stays close to outdoor temperature without AC |
| Fire | Heat detector (not smoke: exhaust sets those off) linked to the house alarms and the guard house; extinguisher by the door | A car or EV fire is found early and the gate knows |
| EV | 7 kW charger on its own circuit with type B residual-current protection, metered and load-managed (§4) | Charging stays safe and inside the estate's grid limits |
| Floor | Sealed, oil-resistant concrete, 150 mm below the house floor, falling to the door | Water and oil drain out, not into the house |
6b. Type C corner house
The house at each end of the two outer rows takes the whole free corner of the site; every size of the estate has exactly four (site-plan.md). It is built to the same specification as every other house (§0 to §8). What differs:
| Item | Spec | Why |
|---|---|---|
| Plan | Type B's plan enlarged: 15 m wide (Type B 12 m), 5 bedrooms and 5 bathrooms, about 300 m² on two storeys; 6 AC units, 7 DC ceiling fans, a larger ERV | A house for the families who would otherwise rent a pool villa |
| Plot | Corner plot of 715 to 1,053 m² on the flagship (897 m² on average; 838 to 942 m² on average in the 20- to 50-house variants), running on to the green belt at the west corners and to a 4 m path gap at the club at the east corners. The house stands 3.5 m inside its inner plot line | Uses the corner the row leaves free; 7 m to the neighbour, as between all houses |
| Garage | 9.5 × 6.0 m inside, three cars side by side, two insulated sectional doors (6 × 2.5 m and 3 × 2.5 m) with motors and app control; otherwise as §6a | Three cars under a roof, no carport in the corner garden |
| Pool | 8 × 4 m skimmer pool on the corner side of the house (beside the house where the plot is wide enough, otherwise in the back garden), salt chlorination, variable-speed pump | Salt cell instead of stored chlorine at the house; the variable-speed pump runs in solar hours under the estate's energy management (§4) |
| Pool safety | Pool fence with a self-closing gate between the house and the pool, safety cover, non-slip deck, outdoor shower | Tenants with small children; the cover also keeps leaves and rain out when the house stands empty |
| Pool care | The estate team cares for the pool weekly as part of full service: water balance, salt, cleaning, filter, top-up; the tenant never handles chemicals. In the model, care and chemicals about 36,000 THB a year (est.) and a pool reserve (pump, filter and salt cell every 8 years, resurfacing every 15, est.) | Same rule as for the rest of the house: the tenant never maintains anything (operating-model.md) |
| Allowances | Electricity 800 kWh a month including the pool pump, water 50 m³ (Type A 500 kWh and 30 m³) | A normal month costs the tenant nothing |
| Cost | Pool 950,000 THB (est.), inside the 840,000 to 1,030,000 THB quoted for small and medium skimmer pools in Thailand;[73] deck, fence, cover and shower 150,000 (est.); the Type C all-in cost and rent are in costs-and-rent.md |
A circulated, chlorinated pool is not the standing water the estate avoids (engineering judgement); the team checks it with the rest of the estate's drains and gutters every week, and keeps it running between tenancies.
7. Life safety and security
- Interlinked smoke / heat / CO alarms, extinguisher and fire blanket in the kitchen.
- Laminated glass and multipoint locks on every ground-floor opening.
- Video intercom: door station with camera at the front door, indoor station with touch screen and SOS button by the entrance, app for the tenant's phones; linked to the guard house master station over the estate network (SIP), no camera inside the house, calls not recorded.
- Gated estate: perimeter wall, one staffed main gate with plate cameras and card readers, CCTV at the gate and along the wall (security-and-access.md).
8. Verification (what makes the spec real)
Every house gets, before a tenant moves in:
- Blower-door test result (n50 ≤ 0.6 /h) and the house's Passive House certificate.
- Thermographic scan of walls and roof.
- ERV commissioning sheet: flows balanced, filter classes confirmed, overpressure in smoke mode measured.
- Electrical test certificate and plumbing pressure test record.
- PV, sub-meter and leak shut-off commissioning; an islanding test showing the house stays on when the estate runs on its battery; first month of monitored data.
- A one-page "house passport" for the tenant with these results.
At every change of tenant the estate repeats a blower-door spot check, logs the filter and service dates and updates the passport.
These results are also the marketing: a tenant can see indoor PM2.5 on the dashboard during smoke season.