Comfort and strategies
Move over the chart to read a state of the air.
Click two states of the air to draw a process between them.
When each strategy is needed
Every hour of the year, hour of day against day of year, in the colour of the strategy that makes it comfortable (the numbers and colours of the table and the chart).
Strategies
Design guidelines
Bioclimatic potential Olgyay's chart, after Košir and Pajek (BcChart)
Each month is a line from its mean daily minimum temperature at its mean daily maximum humidity to its mean daily maximum temperature at its mean daily minimum humidity; the share of the line in each zone is the share of the month. With the sun, the warm end of a month is raised by what the mean irradiance of its sunny hours does for a body in the sun (Olgyay's heat balance), never past the top of the comfort zone (dashed blue), and passive solar heating counts only down to the temperature the month's peak sun can bring to comfort. A monthly reading of the climate, for the first choice of passive measures: not hours, and not a building. After Košir and Pajek, BcChart v2.0 (ISES 2017); zone outlines digitized from their chart by this tool.
Building form for this climate archetypes, from the Mahoney tables
The Mahoney tables for this weather file
What the tables recommend
Forms compared by simulation
Rules of thumb for this climate
Local codes and standards
What the building code and the standards of this place ask, where it bears on climate and concept design. A summary to start from, not legal advice: read the source before relying on a value.
Temperature hour of day against day of year in the maps; the scales are the same for every climate
Temperature by month
Degree days
Ground temperature
Sun and sky
Sun on a horizontal surface
Sun path
Every hour with the sun up, by where the sun stands: on the left as compass direction against height, on the right the sky seen from above (north up, the zenith in the middle). Under 20 °C the sun is welcome, from 20 to 27 °C shade helps, over 27 °C shade is needed: what a shading device should block and what it should let pass. Radiation benefit colours each hour by its direct sun (W/m² normal to the beam): blue where it is welcome, red where it is not, pale where it is weak or the air is between 20 and 27 °C. Orthographic keeps the high sun spread out and crowds the low sun at the rim; stereographic gives the low sun more room, as on most printed sun path diagrams.
Sun angles for this site
Daylight outdoors
Daylight factor indoors EN 17037, for this climate
Check a room lit from one wall
Sky cover
Sky type from the sun in the file
What the sky asks of daylighting
Each daylight hour (sun over 5°) is classed by the Perez clearness index ε, from the file's diffuse and direct sun and the sun's height (Perez et al., 1990): the index behind the Perez all-weather sky and the CIE general skies of ISO 15469. Perez's eight bins are grouped here in three, overcast under 1.23 and clear from 4.5; the grouping is this tool's. The CIE sky idea follows Andrew Marsh's sky tools; written here from the published model.
Orientation and form: sun on the facades
Shading benefit by orientation
Noon sun at the solstices and equinoxes: the overhang section
The textbook section for the facade that looks toward the equator: the three noon sun angles of the year follow from the latitude alone (90° less the latitude, plus or minus 23.45°). It is a first sizing by geometry; the cards below weigh every hour of the weather file and every orientation.
Optimal shading angles by orientation
Each facade is drawn twice: from the side (section) and from above (plan). The wedges show where the sun stands in the sky as that facade sees it. Orange is sun that arrives when the building is warm and should be shaded; yellow is sun that arrives when it is cold and is worth keeping. A fixed device works when it can cover the orange wedge without covering the yellow one; where the two overlap, only movable shading can tell them apart.
Direct sun on the facade in kWh/m² a year. Left and right as seen looking out; in the drawings the building, the glass and the shading device are in grey and black, with the device's cut-off ray dashed; colour is kept for the sun. The shaded wedges are where the sun stands, as seen in section and in plan, for the middle 80 % of the sun to shade (orange) and of the sun to keep (yellow).
A horizontal device (overhang, louvres) shades the glass wholly when the sun's profile angle is above its cut-off; its depth is that share of the window's height (for louvres, of their spacing). Vertical fins shade wholly when the sun stands further to their side than the cut-off, given for each side. The cut-offs are those that take the most sun to shade for the least sun to keep; “takes” and “costs” are shares of each. Pick a facade above the sun path chart to see its mask.
Solar energy by tilt and direction
Test a window and its shading every hour of the weather file
Red: hours over 27 °C when sun still reaches the glass. Blue: hours under 20 °C when the device keeps welcome sun off it. Green: sun on the facade, but neither. The deeper the colour, the more sun (kWh) at stake.
One window on one facade, with an overhang, a fin on each side and horizontal louvres, each sized here. The share of glass in sun comes from 1,200 points on the glass, each tested against the sun of every hour (to about 2 %). Solar gain is the glass area × its solar factor g × the sun on it: the direct sun that gets past the device, plus the diffuse sky and ground light, which the device is taken not to cut. Hot and cool are the page's bands: over 27 °C and under 20 °C. Inspired by the window tools of susdesign.com; written here from solar geometry and the weather file.
A building opposite the sun and sky it takes from a window
A long building parallel to the facade, its top the given height above the window's centre. Sun is lost in an hour when its profile angle is under the obstruction's. The vertical sky component is the CIE overcast sky's light on the glass as a share of the open sky's on the ground, sky only (BRE, Site layout planning for daylight). The idea follows Andrew Marsh's overshadowing tools; written here from solar geometry, the CIE sky and the BRE method.
Wind and air
The file's wind is measured at 10 m over open ground. Over rougher ground the same weather gives less wind near the ground and the full speed only higher up (power law of the boundary layer, terrain values after ASHRAE Fundamentals). Mean speeds: gusts and the flow around buildings are not in it.
Natural ventilation potential by month
Natural ventilation potential, hour by hour
After Causone (2016): outdoor air at least this warm and no warmer than the day's adaptive comfort limit (ASHRAE 55, neutral temperature plus 3.5 K), with its relative humidity within the range. Indoors, the air's moisture is taken at the room's temperature, so cool damp air that warms up on entering still counts.
Wind comfort (Lawson)
Driving rain on the facades
Humidity and rain
Rain
Outdoor comfort
Outdoor comfort: Universal Thermal Climate Index
The four conditions compared share of the period's hours in each category
Hours under and over the limits
What to provide outdoors, for the period and by season
In the sun: a standing person in the open, with the sky's and the sun's radiation. Under cover: surroundings at air temperature. In the wind: the file's wind at 10 m. Sheltered: 0.5 m/s. Activities count the hours within fixed limits of the index: sitting 9 to 26 °C, walking 0 to 26 °C, play and sport −13 to 26 °C.
How each variable moves the index air temperature against humidity, radiant temperature and wind
Each map varies air temperature and one other variable; the other two stay at the references set above, and the dashed line marks the reference of the map's own variable. "Change from the reference" is the index at a point minus the index at the same air temperature with that variable at its reference. Grey: outside the range of the index's polynomial (radiant minus air temperature from −30 to 70 K, vapour pressure up to 5 kPa); wind is held between 0.5 and 17 m/s. Dots: the open file's hours whose other two variables lie near the references (humidity within ±10 %, radiant minus air within ±5 K, wind within ±1 m/s), so the colour under each dot holds for that hour; their number is at the top right of each map. Radiant temperature is that of a person standing in the open.
Building envelope first sizing from the climate alone; no building is simulated
Prescriptive envelope for this climate zone
Prescriptive assemblies insulation by class of construction
Glazing by facade
Insulation
Glazing specification by facade
Thermal mass
Time lag of a wall
Technologies and a warmer climate
Active systems and what this climate gives them
Indications from the weather file alone. Heat pumps are taken at 45 % of the ideal performance with water at 35 °C; photovoltaics at 20 % efficiency and a performance ratio of 0.8.
Photovoltaics built in: which technology where
Another technology comes first than by energy per m²: the ranking depends on the measure. Click a row for every technology that suits it.
How it is worked out, and what is assumed
What a module receives in each urban setting was traced beforehand by ray tracing, with no climate in it: per sky patch, angle of incidence and kind of reflected path, and the sun on each of its cells. The climate's part is worked out here from this weather file, so it follows the scenarios and the measured years. A module's light by its angle, colour (the site's spectra after Bird and Riordan's model; the cells' responses from their layers' optics or band gaps) and level; its temperature from a heat balance with the wind at its height in the setting; partial shade by how its cells are connected; then the converter that gives most of four (string, optimiser, micro, submodule). Carbon over 60 years: modules and electronics made as often as they wear out, against the element they replace and the electricity they keep from the grid (Ember's life-cycle factor of 2025 via Our World in Data, Europe only; the European Union's mean for European files without their own). Each kWh counts as displacing the grid's: self-consumption and storage are not in it. Many technologies have generic figures for their response to light and temperature (evidence: measured, datasheet or generic, listed per technology): the ± is one standard deviation that follows from it. The settings are idealized blocks on a grid of streets; the elements replaced and the mountings' heat loss are assumptions of typical magnitude.Cost-optimal and zero energy: what a house costs over the years
How it is worked out, and what is assumed
The EU cost-optimal method (Directive 2010/31/EU, Delegated Regulation 244/2012, EN 15459) as Leutgöb, Pagliano and Zangheri applied it (Cost optimality: brake or accelerator on the way towards nearly zero energy buildings, eceee Summer Study 2013, Politecnico di Milano, eERG): every combination of measures is costed, and the cheapest packages in each band of energy, smoothed to their lower convex hull, draw the curve. Discount rate 4 % and energy prices rising 2.5 % a year, both real, are their financial perspective (Table 6). The house, its measures, their costs and lives are the JRC's new-house prototype for Milan (D'Agostino and Parker, A model for cost-optimal simulation of new nearly zero energy buildings in Europe, JRC106218, 2023, CC BY 4.0, Tables 4 to 6): 120 m² on two storeys over a cellar, gas boiler, mini-split cooling, ventilation with heat recovery; prices €0.25/kWh for electricity and €0.058/kWh for gas, and photovoltaics at €3,621/kWp (its 4 kWp for €14,484). Costs are the extra over the base house; the base house itself is put at €1,000/m² (Pagliano's Table 6). Primary energy factors 2.06 for electricity and 1 for gas (the same table, 2020). Energy of each package by the monthly method of EN ISO 13790 from this weather file, so it follows the scenarios and the measured years. Each line adds a year of running cost, discounted; no residual value is counted. With energy only (as in the cost-curve figure) a year is the energy bought less the surplus sold, so the lines meet near zero energy; not exactly, since zero primary energy is not zero cost (gas is bought, the surplus electricity sold for less). With maintenance and replacements, as Regulation 244/2012 counts the global cost, 1 % a year of the plant's cost and each part again when its life ends are added: the photovoltaics, replaced after 25 years, then keep the lines apart at zero energy, and the optimum moves towards using energy. Assumed here, not given by the JRC: the plan (10 x 6 m, long sides north and south), U-values and g-values of the windows, the cellar's heat loss, shading of the east and west windows by the neighbours, the energy of appliances and lighting, infiltration as n50 / 20, and the hot water's solar share. Checked in Milan: the base house's electricity is within 2 % of the JRC's, its heating gas 20 % above; the final package uses 27 % less gas, and photovoltaics give 1,117 kWh/kWp here against the JRC's 883. The energy classes under the axis are those of the cost-curve figure this card follows, not an official scale of the file's country. Heat pumps and the pellet boiler are costed from the Danish Energy Agency (Technology Data for individual heating plants, data sheets of April 2026, CC BY 4.0; 2025 prices without VAT), as their extra over its gas boiler and gas line; their seasonal efficiency is the agency's for radiators, scaled to this climate by the ratio of Carnot efficiencies to Copenhagen's. Pellets at €0.07/kWh and a primary energy factor of 0.2 are assumed. Electricity netted over the year is kind to heat pumps with photovoltaics: their winter demand is not met by the summer surplus hour by hour.A warmer climate, or another file
A warmer year is this file with every hour raised by the same step and its moisture kept: a sensitivity, not a projection. For a projection, load a morphed future file of the site as the other EPW.
Zones after Givoni, as drawn in Figure 8 of “Active and Passive” (Lightweight Energy). A pre-design reading of a climate, not a simulation of a building.
Sources: weather files from EnergyPlus.net and Climate.OneBuilding.Org; the station list from the CBE Clima tool (MIT licence); the UTCI polynomial (Bröde et al., utci.org) as listed in pythermalcomfort (MIT licence); map data © OpenStreetMap contributors, tiles by OpenFreeMap; place search by Nominatim.