The Tarnwick Energy Co-op · Harborn & the Saltmeadow shore · member-owned
Warm houses are a neighbourhood project.
Tarnwick is four hundred households around Harborn who weatherize one another’s homes at cost plus wages — blower-door diagnostics, dense-pack walls, attics to R-60, heat-recovery ventilation, and a scope read aloud at the monthly meeting before a dollar of it moves. Members crew the van, the ledger publishes twice a year, and nobody’s dividend is your fuel bill.
The co-op promise
What membership actually is
A one-time share of $120 that comes back if you leave, a monthly meeting where scopes are read aloud before they are signed, and the right to crew the van yourself under the foreman — several members have packed cellulose into their own kitchen walls at member rates. The co-op exists because the shore’s heat-loss problem is a street at a time, not a house at a time, and because a contractor’s margin is a terrible thing to pay for January.
The open ledger
Every scope, wage and material cost publishes to the membership twice a year, and any member may audit the books at the AGM. Rates are cost plus wages — nothing else — and if the co-op ever runs a surplus it goes to the next street’s retrofit fund, not to a dividend.
Services
What the crew runs
01
The co-op diagnostic — $95 to members
Blower door and infrared with the whole household invited to watch, plus both readings and the images in the file the co-op keeps for your house. The diagnostic van runs two evenings a week and Saturdays, member bookings first.
02
Dense-pack collective days
Three houses on one street, one machine, one trained crew and whatever members have signed on to help: cellulose at 3.5 lb/ft³ through 2-inch holes, plugged and patched the same day, and the machine does not leave the street until all three walls are quiet.
03
Attic days to R-60
The vacuum, the dams, the baffles and the blow — done once, done deep, with the joists gone from sight and the hatch card signed by whoever crawled it. Member attic days are scheduled in the survey round each spring.
04
Ventilation installs
HRVs and ERVs commissioned and balanced with the co-op’s own flow hood, filters and cores on the service round, and the commissioning sheet filed with the house. Tight houses on the shore breathe on purpose now, and the windows are the proof.
How it goes
A membership year, season by season
The same sequence on every job — the only variable is your project.
Spring
The survey round
The diagnostic van tours the streets that asked for it at the March meeting. Readings, images and drafts of scopes go into the spring file — every house measured before anything is promised.
June
The scope meeting
Scopes are read aloud, questioned and amended — including the prices. A street can vote to bundle its houses into a collective day, and usually does.
July — September
The work season
The long days: sealing, dense-pack, attic blows, ventilation installs, member crews alongside the trained ones, and the ledger updated as each job closes.
October
The test-out round
The blower door comes back to every house the season touched. Second readings print on the invoice beside the first, and the cohort’s numbers go on the AGM slide.
November
The accounting
Books published, wages and materials reconciled to the penny, surplus routed to next year’s street fund — and the first cold snap arrives to a shore that reads better than it did a year ago.
Harborn & the Saltmeadow shore
The 2025 work season
Six jobs off the season’s ledger — collective days, attic days and one whole street — photographed at the test-out with the cohort’s numbers read out at the November accounting.
Cost plus wages
Member rates, published
Cost plus wages, published twice a year — the same rates for every member household, and the difference credited back if you join after the work. Non-members are welcome while capacity lasts; the co-op was founded on the theory that neighbours who can see the books stop wondering about the bill.
Member rates, 2026
Co-op diagnostic$95
Blower door, infrared, written scope — the member rate
Dense-pack walls$3.90 / sq ft
Crew of six on a collective day, materials at the co-op’s price
Attic to R-60$1.95 / sq ft
Vacuum, dams, baffles, hatch seal and the blow
Air-sealing dayfrom $760
Every hole the camera names, sealed in one visit
HRV / ERV install$2,700–4,000
Commissioned, balanced, service book included
Non-member rate+15%
Everything above, before you join — join and the difference is credited back
Six of us crewed the van the day it came to our street — I packed cellulose into my own kitchen wall under the foreman’s eye, by the book, and paid member rates for the material. The February bill was the lowest on the street and the ledger says exactly why, to the penny. It is the only home improvement I have ever been proud of the way you are proud of a barn.
We joined for the rates and stayed for the meetings. Our 1958 semi tested 3,300 CFM50 at the survey; after the collective day and the attic blow it read 1,450, and thirty neighbours have now watched that number close like a scoreboard.
The scope meeting is the most accountable thing I have ever watched a tradesperson do — the prices read aloud, a retired accountant in the second row, and my chimney gap questioned into a smaller bill. Then they did the work and the reading beat the scope.
Two streets over had it done the year before, so we had twelve months of other people’s fuel bills to read before we spent anything. That is what a co-op sells: evidence with your postcode on it. The HRV went in in August and the windows were dry by the first frost.
Before the meeting
Co-op questions
The five the books desk answers every week. Anything stranger goes to the monthly meeting, where it gets thirty seconds and usually a volunteer.
Do I have to crew the van?
No — most members never lift a hose. Crewing is a right, not a duty: those who want the training get it, those who want their Saturday back get that. About one member in eight turns out for a collective day, and the work does not depend on it.
What if I am renting?
Landlords may hold the membership and the share, but tenants may book the diagnostic and bring the results to whoever holds the lease — half the shore’s retrofits started as a tenant with a reading and a conversation. The co-op’s scope format is written to survive that conversation.
Is the quality actually any good?
The trained crew leads every job and signs every test-out; member labour carries and fetches under supervision. The 2025 cohort’s median CFM50 cut was 41% on sealing-and-filling scopes — measured by the co-op’s own blower door and printed in the accounts.
What happens to my share if I move?
It transfers with the house at no cost if the buyer joins, and redeems at face value if they do not. The file of readings and images transfers either way — the house’s history belongs to the house.
Can the co-op do my whole street?
That is the design. Streets bundle through the June scope meeting: three houses makes a collective day, a whole close makes a season. The machine does not leave until the street is quiet, and the ledger shows what that saved.
The autumn scope meeting is the third Tuesday of September — members and the merely curious both welcome · (555) 077-6439 · books@tarnwickenergy.example
Join and book
Tell us the street and the decade the house was built — membership is a $120 share, the diagnostic is $95, and the scope gets read aloud at a meeting you are welcome to attend before you sign anything. books@tarnwickenergy.example